# Best armed fighter



## renrich (Dec 12, 2008)

The early war fighters such as Hurricane and Spitfire were armed with rifle caliber MGs which offered a high rate of fire but not great hitting power. They also had a rather limited supply of ammo. The German and Japanese armed with a mixture of cannon(with explosive shell) and rifle caliber MGs. The cannon had not a lot of ammo but the MGs had impressive amounts of ammo. As the war wore on fighters carried more cannon and heavier MGs. Considering the enemy likely to be encountered what was the best armed piston fighter that served in WW2.


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## Kurfürst (Dec 12, 2008)

The Focke Wulf 190 without doubt. Plenty of guns, four of them cannons, most of them close to the centerline, and with lots of ammuntion - IIRC some 1800 rounds of 7.92mm and 500 to 750 rounds of 20mm is a hulluva lot of firepower. In fact the outer cannons were often removed, the inner two with 500 rounds of cannon were generally enough to deal with most enemy aircraft. And if not - well, just put back those cannons again!


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## DerAdlerIstGelandet (Dec 12, 2008)

I do not think there is a 100% correct answer to this question. It depends on what mission the aircraft was used for.

For fighter to fighter the .50 Cal was eneogh but for bomber killing the German aircraft were typically armed better.

I think it has to be broken down into more catagories.


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## lesofprimus (Dec 12, 2008)

The Fw 190A-8 with its 4 MG 151/20's and 2 MG 131 has got this pegged....

For a fighter verses fighter comparison....

If we are talking on ANY air to air mission, the Me 262 has to be the winner, with those 4 30mm Mk 108 cannon loaded with minen rounds...... Second place goes to the 190A-8/R8 with 2x 30mm, 2x 20mm and 2x 13mm....

Some may argue the Tempest and its 4x Hispano Mk. V 20mm, but the extra 13mm's on the A-8 makes it tops...


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## kool kitty89 (Dec 12, 2008)

The Fw 190 also had a lot more ammo in the inboard cannons and though the MG 151/20 fired a less powerful cartridge, it made use of the high capacity shells. (with the HE(M) shells having roughly double the capacity of the Hispano HE/I shells)

And the the 13mm and inboard 20mm's were on the centerline, concentrated and without a convergence zone. (albeit rate of fire was reduced somewhat due to synchronization)


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## Waynos (Dec 12, 2008)

The Bristol Beaufighter was the most heavily armed fighter wasn't it? with 6 .303's and 4 20mm hispanos.


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## Juha (Dec 12, 2008)

I'd say FW 190 from A-6 onwards, Me 262 was a jet, and Tempest Mk V. 4 Hispanos were surely enough against targets Tempests met, single-engined and twin engined almost exclusively, incl lot of V1s. MG 131 wasn't very powerful HMG, if 4 MG 151s were not enough the MG 131s didn't add much firepower and if one run out MG 151 ammo the two MG 131 didn't give much firepower on 44/45 standards. Mitsumishi J2M3 had also 4 20mm as had N1K2-J, in fact also N1K1-J.

Juha


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## Juha (Dec 12, 2008)

As for night fighters, four 20mm was enough and because LW bombers were lighter so Mossie NF or Beau NF or P-61, Japanese bombers were not ultra tough. Ju 88G's 4 20mm was also clearly enough and those upward firing 20mm gave extra flexibility. In the end I'd say Ju 88G (4*20mm forwards + 2*20mm upwards + one MG 131 flexible dorsal) Do 217 NFs had 4 MG 17s more but I'd say they didn't matter.

Juha


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## Grampa (Dec 12, 2008)

If you talking about maximum firepower, look at the Heinkel He 219 Uhu


_View: https://www.youtube.com/watch?v=4FLEnG07pXE_


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## syscom3 (Dec 12, 2008)

Going by Adlers comments ..... for air-to-air, I would say the 8x.50's of the P47 or 4x.50's of the P38 were quite devastating.


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## kool kitty89 (Dec 13, 2008)

Don't forget the P-38's 20mm cannon. Desipite the reliability problems with the US Hispano, I rember reading that pilots apreciated the added firepower of the cannon. 

ANd the ammo capacity of the .50's was pretty high at 500 rpg.


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## magnocain (Dec 13, 2008)

One could argue that is was the B-25h or B25j with .50x10+75mm or .50x14MGs firing forward.
But they weren't really fighters, now were they...
I would not like to face the Hurricane's .30x12 either.


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## Kurfürst (Dec 13, 2008)

Fritz Hahn makes a pretty interesting comparison between the 12 x 7,7mm (.303) configuration vs 2 x 20mm on the FW 190A-4/U8. 







In brief, at equal installation weight, the two 20mm cannons deliver almost double the weight of fire (4,92 kg/sec vs 2,77 kg/sec), and 0,89 kg of explosives to the target per second.


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## renrich (Dec 13, 2008)

One consideration in judging armament would be the chances of getting hits because of variables such as rate of fire, trajectory and projectile dispersion. It would seem that the P38, with all guns mounted in the nose would have a good concentration of fire. Another factor to consider would be the effect that guns firing through the propellor arc might have a slower rate of fire. Chris is right about the mission having an impact on judging armament which is why I said "considering the enemy to be encountered."


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## Juha (Dec 13, 2008)

I agree, Renrich
that's why I didn't mentioned He 219, IIRC many LW NF aces didn't like 30mm cannons, they were too effective. At night there were not much joy on the long range of MK 103, on the other hand it was heavy. Because when using forward firing armament the best approach was from behind and below, both MKs had too powerful shells, risk of hitting debris was rather high. And as upward firing weapon MK 108 increased the risk that the target lost its wing and plumbed onto attacker, that's why many aces prefered MG FF as upward firing weapon, its shells had enough destructive power but were not overkill.

Juha


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## Waynos (Dec 13, 2008)

How was a P-38, with 5 guns, one of which was a 20mm cannon, better armed that a Beaufighter with 10 guns, four of which were 20mm cannon?


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## 109ROAMING (Dec 13, 2008)

I agree with Adler

To have the best armed fighter depends solely on the mission

For taking on bombers I think The Fw-190 A-8 sounds good ,canons have good destruction properties

Fighter to fighter I think 6*.50 sounds good as of the P-51 ,High rate of fire

Air to ground ,Well that depends on what your wanting to take out but most likely you'd want something powerful eg 4* 20mm as of the Typhoon/Tempest

my 2cents anyway


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## syscom3 (Dec 13, 2008)

Waynos said:


> How was a P-38, with 5 guns, one of which was a 20mm cannon, better armed that a Beaufighter with 10 guns, four of which were 20mm cannon?



Because the Beaufighter wasn't a true fighter.


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## syscom3 (Dec 13, 2008)

109ROAMING said:


> Fighter to fighter I think 6*.50 sounds good as of the P-51 High rate of fire



But the P47 had eight of them. And while the P38 only has four, there are no convergence issues.


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## renrich (Dec 13, 2008)

On paper, the Beaufighter, with 10 guns, four of them 20MM, would be very formidable, especially against enemy bombers, if it could get into firing position. However, the six 303s would perhaps not be all that effective against the tougher airplanes. Against enemy fighters, because of performance issues, the P38 might be better armed because the four 50s concentrated in the nose and with the P38 performance perhaps would give the P38 the edge with the 20MM being the icing on the cake. I am certainly not postulating the P38 as the best armed piston fighter but rather speculating about how all the armament clustered in the nose might give it more hitting power than similarly armed AC with wing mounted guns. Were the 303s on the Beaufighter wing mounted?


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## claidemore (Dec 13, 2008)

Beau-FIGHTER? Designed as an interim replacement until the Whirlwind could be fully developed, and classified as a "heavy fighter". Started it's career as a night fighter, then fighter/bomber, and eventually went on to be used in the anti-shipping role. 

The four 20mm Hispano cannons on the Beau were in the nose, the six .303s were in the wings, four on one side, two on the other (outboard of the engines). The Mosquito MkII had four 20mm plus four .303, all mounted in the nose, giving it an even tighter concentration of fire, albeit with two less machine guns. 

The Mk21 Beaufighter had four x 20mm (nose) and four x .50 Brownings (in the wings). That's pretty hard to beat.


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## HoHun (Dec 13, 2008)

Hi Renrich,

>Considering the enemy likely to be encountered what was the best armed piston fighter that served in WW2.

Well, here is a comparison of raw firepower (in terms of firepower at the muzzle, international decimal separator):

Me 262: 20,1 MW
Fw 190A-8/R2: 13 MW
Ta 152H: 7,6 MW
Fw 190A-8: 5,5 MW
Me 109K-4: 5,5 MW
Beaufighter Mk 21: 5,3 MW
Tempest: 4,9 MW
Fw 190A-4: 4,3 MW
Typhoon: 4,2 MW
Spitfire IXE: 2,7 MW
Spitfire VC: 2,5 MW
P-47D: 2,3 MW
P-38: 2,2 MW
Me 109G-6: 1,8 MW
Me 109E-4: 1,7 MW
P-51D: 1,7 MW
Me 109G-2: 1,4 MW
P-51C: 1,1 MW
Hurricane IIA: 1,1 MW
Spitfire II: 0,7 MW
Me 109F-2: 0,6 MW
Me 109E-1: 0,3 MW

Rate-of-fire losses through synchronization are not included, but with an electrical system as used by the Luftwaffe should be around 5 % - 10 % depending on type of gun and current flight parameters.

(The MG 151/20 installed have been considered to be using standard ammunition, not the more powerful late-war MX ammunition.)

With regard to wing armament, below a diagram showing the impact of off-centre gun placement and higher dispersion in the P-38 vs. P-47 comparison for their 12.7 mm MGs only (P-38 cannon not considered) for a "zero allowance" shot (placing the aiming dot right on centre of the fighter sized target). As can be seen from the graph, the four guns of the P-38 really give superior hit power for most ranges except the convergence distance of the P-47's eight-gun battery.

My pick for the best-armed piston fighter of WW2 is the Ta 152H as it combines high firepower with centreline weapon placement.

Regards,

Henning (HoHun)


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## bigZ (Dec 13, 2008)

Although it didn't reach production the Martin Baker MB3 would have been formidable with 6 x 20mm.


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## Graeme (Dec 13, 2008)

HoHun said:


> Well, here is a comparison of raw firepower (in terms of firepower at the muzzle, international decimal separator):
> 
> *Me 262*: 20,1 MW



So, we have the winner here?


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## renrich (Dec 13, 2008)

Most interesting data being furnished here. Many thanks to all. As those of us who hunt know and, especially, those who handload, ballistics at the muzzle are not as important as ballistics downrange where the projectile has to do it's job. I am not up to figuring out what the ballistics at a range of 300 yards would be. Can you, Henning, furnish those. Obviously, another factor plays a big role. In Lundstrom's books he mentions often that the 30 cal bullets from an A6M would usually be defeated by self sealing tanks. However, the 20 MM cannon round would usually puncture and tear up the SS tanks. However, the early war Zekes only carried 60 rds of 20 mm and since they had a low MV, they were somewhat difficult to hit with. Does anyone know if the 50BMG would defeat a SS tank? One candidate for a well armed fighter against bombers might be the P61. Four 20 MM cannon and four 50BMGs firing at 800 RPM all on the center line.


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## syscom3 (Dec 13, 2008)

But when you're outside of convergence point, all of those projectiles are going to be less and less effective.


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## kool kitty89 (Dec 13, 2008)

Hennning, why does the MK 108's hitting power dip downafter 200 m but then jump back up at 500 m?


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## HoHun (Dec 13, 2008)

Hi Koolkitty,

>Hennning, why does the MK 108's hitting power dip downafter 200 m but then jump back up at 500 m?

That's the result of putting the aim point directly on the centre of the target. The projectile takes a curved trajectory that takes it above the aim line, and in conjunction with the dispersion that causes some shots to go above the centre of the pattern and some below, some of the high shots miss above the target at 300 and 400 m.

At 500 m, the trajectory curves back down so that it's right on target again. However, the trajectory is curved so much that at 600 m and beyond, all shots will miss below the target.

(This is all valid only for a "boresight aim", no compensation approach.)

Regards,

Henning (HoHun)


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## HoHun (Dec 13, 2008)

Hi Renrich,

>I am not up to figuring out what the ballistics at a range of 300 yards would be. Can you, Henning, furnish those. 

Difficult, but I had a look into it a while back. There is not much good data, but two general rules are evident: 

- If you go downrange, shells with a high chemical content keep their energy much better than those without.
- High velocity projectiles lose energy quicker than low velocity projectiles.

As rough estimates from the incomplete data, I figured that the MK 108 mine shell would still have 96 % of its total energy at 500 m, while the 12.7 mm Browning armour-piercing incendiary would be down to 64 % of its muzzle energy.

(These losses are not taken into account in my above Me 109K/P-38/P-47 comparison graph.)

Regards,

Henning (HoHun)


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## lesofprimus (Dec 14, 2008)

Real interesting stuff here fellas.... Surprised Drgondog aint in this...

If we can guys, lets keep this in the boundry of single engined fighters, and those utilized for air to air combat...


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## Lucky13 (Dec 14, 2008)

What was the different armaments of the 190 D's then?


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## renrich (Dec 14, 2008)

If we keep this single engined fighter, it certainly simplifies but excludes P38 and Me110 and perhaps others that were always intended for air to air combat. The P61 was purpose built as a night fighter or all weather fighter and I believe that Beaufighter was designed as a long range fighter. If one takes into account the factor that adding heavy armament to an existing design like the BF109 or Hurricane, etc,. can degrade performance, that can complicate the choice of best armed fighter. In other words, if adding a lot of weapons degrades performance significantly, then maybe that fighter drops out of consideration. In comparing down range ballistics, there are several considerations. I would assume that, in the case of an explosive shell that does not depend on kinetic energy to damage the target, there is no difference in the damage the target suffers at any range as long as the fuse causes the shell to explode. However, perhaps penetration is necessary before the fuse reacts to achieve major damage. But another factor is ballistic coefficient. If a 30 cal bullet starts out at 2800 fps and a 50BMG starts at 2800 FPS the 50BMG soon outpaces the 30 because of it's much better BC and thus reaches the target sooner and has a flatter trajectory which makes range estimation easier and, to boot, the 50BMG is a much bigger bullet so has more kinetic energy and penetrates better because of better sectional density. I don't know what the ballistic coefficient is of the various explosive shells in the 15, 20 or 30 MM projectiles was but I do know that some of the 20 MM shells in the early examples did not have very flat trajectories. An example of a single engined fighter which could carry a heavy and potent armament without much effect on performance would be the models of the Hellcat with two 20MM cannon and four 50 cals.


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## syscom3 (Dec 14, 2008)

If a cannon shell has a more arcing trajectory compared to a MG with a flatter trajectory, then I would say the MG would be more usefull in an air-to-air battle simply because there's a higher probability of the MG projectile to hit its target.


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## lesofprimus (Dec 14, 2008)

Mg's just dont pack the punch of cannon fire tho.... Longer time on target to get the same desired effect as cannon...


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## HoHun (Dec 14, 2008)

Hi Renrich,

>In comparing down range ballistics, there are several considerations. I would assume that, in the case of an explosive shell that does not depend on kinetic energy to damage the target, there is no difference in the damage the target suffers at any range as long as the fuse causes the shell to explode. However, perhaps penetration is necessary before the fuse reacts to achieve major damage. 

The exact mechanism of translating the energy from the projectile into damage of the target differs with the projectile type. There are cases for all projectile types in which the energy fails to be translated into meaningful damage - for example, bullets that punch a clean hole into aluminium skin, or slugs that are stopped by armour plate.

If you wish to be more accurate, the first thing would be a consideration of what type of structure the bullets hit with which probability. 

German WW2 experience was that the largest part of the target area was metal-skinned structure, which is easy to penetrate but difficult to damage badly enough to force down the aircraft. This lead to the development of high-capacity explosive ("mine") shells, which would blow big holes in the skin to destroy the load-bearing capability of the structure.

The "critical areas" of a target would only make up the smaller part of the target area and usually be armoured or otherwise protected. The Luftwaffe also had armour-piercing projectiles capable of attacking these areas, but front-line experience showed that this approach yielded inferior results to the mine-shell approach, and thus the Luftwaffe standard anti-fighter belting became 3 mine shells, 1 incendiary, 1 armour-piercing incendiary for the MG 151/20.

Unlike other air forces that did not have mine-shell type cannon ammunition for a front-line comparison, the Luftwaffe had combat experience both with mine shells and conventional ammunition and could make a combat-result based evaluation. (On a broad basis, I figure - Steinhoff commented on the tactical value of the detailed combat reports which listed the exact ammunition consumption by number and type for each kill.)

Though it's sometimes claimed that the mine shells were designed as anti-bomber ammunition, that couldn't be farther from the truth. They were introduced right in time for the Battle of Britain when RAF Fighter Command was the immediate enemy, and in fact the belting suggested against bombers by the Schießfibel had only 1/3 mine shells instead of 3/5 as "against all other aircraft".

Regards,

Henning (HoHun)


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## HoHun (Dec 14, 2008)

Hi Lesofprimus,

>Mg's just dont pack the punch of cannon fire tho.... Longer time on target to get the same desired effect as cannon...

Absolutely right ... as I'm sure everyone here is aware the Luftwaffe had two variants of the MG 151 in service, the 15 mm high-velocity variant and the 20 mm variant with the well-known mine-shell capability.

The 15 mm variant was a very potent machine gun, and as Tony pointed out on his website, the USAAF did in fact consider production of a copy of the Mauser cannon as a replacement for the 12.7 mm Browning machine gun. (It was referred to as 0.60" HMG in US documents, I believe.)

However, the Luftwaffe switched from the 15 mm to the 20 mm variant almost immediately when the latter became available, and although the weapon could easily be converted from one calibre to another, I'm not aware of any Luftwaffe fighter pilot ever having 15 mm cannon exchanged for his 20 mm guns, or even just mentioned that he'd like to have had them exchanged but wasn't allowed to. Not that they didn't appreciate the high muzzle-velocity - you'll find the 15 mm variant praised for that, too. Yet, no-one ever considered the trade-off against the higher hitting power of the 20 mm variant so important to have his aircraft converted.

Here is a comparison of firepower, muzzle velocity and projectile mass data:

MG 151/20: 0,97 MW, 720 - 800 m/s, 162 - 182 g
MG 151: 0,28 MW, 850 - 960 m/s, 151 - 166 g
.50 Browning M2: 0,18 MW, 860 - 900 m/s, ca. 112 g

(Obviously, the USAAF considered the MG 151 superior to the 12.7 mm Browning M2, or they wouldn't have considered it as their next fighter weapon. In my opinion, it's not really a quantum leap, and I suspect this is the reason it never entered series production in the US.)

Regards,

Henning (HoHun)


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## renrich (Dec 14, 2008)

Maybe I have missed it but what about the ballistic coeffecient of the various cannon rds.? I have read of, in the Korean War, Sabres making kills at high altitudes of 700 yards on Migs. A Marine exchange pilot, a WW2 veteran, witnessing this as a wingman had it explained thusly. At very high altitudes, much higher than where WW2 was fought the 50BMG had a longer effective range because of the thin air and less friction. Not saying the 50BMG is more of a killer than 20MMs or such but trying to find a comparison of relative ease of making hits because of rate of fire, velocity and trajectory. An extreme example is that the RN favored CLs over CAs partly because they believed the high rate of fire of the 6 inch offset the heavier projectile of the 8 inch.


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## Glider (Dec 14, 2008)

My vote would have to go for the Tempest assuming we are sticking to single engined fighters together with the 190 with the extra 2 13mm.
In brute firepower the Tempest would have it but the better positioning of the 190 weapons would make the difference up.
If someone wants to put one in front of the other I wouldn't complain, but personally consider it to close to call.

If we include the Jets, then the 262 has it by some margin followed by the Meteor.


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## renrich (Dec 14, 2008)

What was the armament of the Tempest?


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## Waynos (Dec 14, 2008)

It had 4 20mm Hispanos in the wings, 2 on each side, this became the standard RAF armament, even Spitfires had it.


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## Glider (Dec 14, 2008)

True but they were the Mk V cannons which had a much faster rate of fire.


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## syscom3 (Dec 14, 2008)

Buts there's also the convergence issues, which dictate the probability of a hit outside of the central zone of convergence.

This is where the P38 excells, where you have the high rate of fire of the 4x.50's in a tight grouping over quite a long distance.


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## HoHun (Dec 14, 2008)

Hi Renrich,

>Maybe I have missed it but what about the ballistic coeffecient of the various cannon rds.? 

Here is a comparison of velocities at the muzzle and velocities at 400 m, including the arithmetic average of each pair and the flight time calculated from it (speed loss is roughly linear initially):


```
Weapon                      v0  v400   v_av   T400
12.7 mm AP M2 (36" Barrel) 867   680  773,5   0,52 <- 12.7 mm Browning M2
20 mm API (from AP M75)    750   555  652,5   0,61 <- 20 mm Hispano II
20 mm mine shell           805   424  614,5   0,65 <- MG 151/20
20 mm HE                   705   490  597,5   0,67 <- MG 151/20

Speeds in m/s, Time to 400 m in s
```

The ballistic table for the 20 mm HE shell shows a flight time of 0.69 seconds to 400 m, so the error from assuming linear speed loss is less than 3%. (I don't have full ballistical tables for the Allied weapons, so I use the same linearity assumption for all projectiles for better comparability.)

400 m were chosen because the firepower comparison I posted above shows that this was about the normal maximum engagement range expected by the USAAF, as evident in the way they harmonized their wing guns.

You might have heard of Frederick C. Blesse, WW2 and Korean War veteran and author of the first "fighter pilot's bible", titled "No Guts, No Glory". His comments confirm the short firing ranges I pointed out:

"This business of firing at greater ranges is a popular misconception in regard to Korea. Contrary to much that has been published, the Fighter Pilots who shot down more than an occasional Mig or two, got them around 400-1200 feet just like they did in Europe and the Southwest Pacific during World War II."

>I have read of, in the Korean War, Sabres making kills at high altitudes of 700 yards on Migs. A Marine exchange pilot, a WW2 veteran, witnessing this as a wingman had it explained thusly. At very high altitudes, much higher than where WW2 was fought the 50BMG had a longer effective range because of the thin air and less friction. 

This applies to all projectiles, of course. With regard to the long range kills, Blesse commented in "Not Guts, No Glory":

"But, make no mistake about this -- the pilots still wanted to get exactly where they did in World War II -- six o'clock at 1200 feet or less. It was only lack of aircraft performance and poor judgment that forced him to do otherwise."

Regards,

Henning (HoHun)


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## kool kitty89 (Dec 14, 2008)

Lucky13 said:


> What was the different armaments of the 190 D's then?



The D-9 had the wing root MG 151/20's and upper cowl MG 131's of the Anton, but eliminated the outer wing cannons. (somthing optional on the Antons as well)

The D-11 (of very limited production) eliminated the MG 131's and added 2x outer wing MK 108's.

The D-12 was tested but didn't enter production, it had the D-11's armament plus an additional MK 108 in a _Motorkanone_ mounting.

The D-13 (again, very limited production) had the D-11's armament plus an additional MG 151/20 in a _motorkanone_ installation.


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## HoHun (Dec 14, 2008)

Hi again,

>400 m were chosen because the firepower comparison I posted above shows that this was about the normal maximum engagement range expected by the USAAF, as evident in the way they harmonized their wing guns.

To further reinforce this point, RAF report "2nd T.A.F./O.R.S. Report No. 43" (which I unfortunately dont' know in its entirety) lists 482 combats as reviewed from RAF gun camera films from Spitfire and Tempest fighters.

Of the 272 "destroyed" claims resulting from these 482 combats, 86 % were from combat distances of 400 yards or less.

The table (1 - 2 % inaccuracy due to rounding in the original report):

600 yards and less: 96 %
400 yards and less: 86 %
300 yards and less: 74 %
200 yards and less: 52 %

So any trade-off improving effectiveness at short ranges is going to have a benefit much greater than the disadvantage at long ranges can be because (just as Blesse pointed out) it's short-range fire that is responsible for the vast majority of kills.

Regards,

Henning (HoHun)


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## beaupower32 (Dec 14, 2008)

My input would be the P-47. 8 .50 cals would just sling a wall of lead torwards anything.


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## claidemore (Dec 14, 2008)

syscom3 said:


> Buts there's also the convergence issues, which dictate the probability of a hit outside of the central zone of convergence.
> 
> This is where the P38 excells, where you have the high rate of fire of the 4x.50's in a tight grouping over quite a long distance.



AN/M2 Brownings had a rate of fire of 750-850 rpm. 
Hispano Mk II had a rate of fire of 650 rpm. 
Hispano Mk V had a rate of fire of 750-800 rpm. 

I think I'd rather have the four Hispanos. 

From: WORLD WAR 2 FIGHTER GUN EFFECTIVENESS



> To return to the obviously controversial question of the relatively poor performance of the .50 Browning: as has already been stated in this study, "the preferred US armament fit [of six or eight .50 HMGs] was effective for its purpose, but not very efficient by comparison with cannon".


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## Watanbe (Dec 15, 2008)

The P38 has to be considered purely due to the nose configuration of its armament. 

For single engine fighter, I like the setup of the Tempest!


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## Glider (Dec 15, 2008)

For those who prefer the P38 the Whirlwind beats it into a cocked hat.


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## kool kitty89 (Dec 15, 2008)

Assuming you have cannon with good synchronizing characteristics (like the MG 151 or ShVak/B-20, possibly an electrically promed Hispano) 2 cannons in the nose plus 2 in the wing roots is a good configuration. (with a motorkanone, guns in the upper cowling may be less desirable due to possible copetition for ammo space, not a possibility with radial enges though)

Even with the significantly reduced rat of fire of synchronized .50 Browning derivatives (ie Ho-5 20mm) I think the centerline configuration is still advantageous. In addition to added firepower at most ranges, albeit less than others due to the poor synchronized performance, but also meaning less weignt in the wings and thus a better roll rate as well as more flexibility of the wing design and possible underwing stores. Also less ammo is needed to acheive the same results. 
(the Finns also mounted 4x .50 BMG in the cowling of their Myrsky)


I think the P-38 can be compared to the single engined fighters, itsself being a single-seat fighter and certainly capable of competing in air to air combat. I would tend to agree that nightfighters and multi-steat "heavy fighters" (Beaufighter, Mossie, P-61, Bf-110, Me 210/410, Ki-45, F7F etc.) are not really comperable.
The only other operational twin that was a "true" fighter that I recall would be the Whirlwind, though it wasn't that widely used. (of course there were prototypes of some very promising contemporaries like the Fw 187, Gloster G.39 -F.9/37- "Reaper" as well as Grumman's F5F and XP-50 and several Designs by Supermarine)


Had the US not had the reliability issues with their Hispano, the P-38 could probably have mounted 4x 20mm cannon in the nose without difficulty.


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## HoHun (Dec 15, 2008)

Hi Koolkitty,

>Also less ammo is needed to acheive the same results. 

Good point. 

With regard to ammunition supply, there is another old misunderstanding that needs to be addressed: Cannon armament does not translate into a smaller ammunition supply.

This erroneous conclusion is based on the comparison of firing times, which of course is inaccurate - 20 shot are 20 shot, and if you're firing them from a muzzle loader, you don't have any advantage over a guy who's firing them from an assault rifle just because it takes you longer to do so.

Everything else the same, long firing time (or "ammo duration", as it's sometimes put) simply equates to "poor firepower", as illustrated by the muzzle loader example.

Here is a comparison of the mass efficiency of various rounds, showing mass of the complete cartridge (including belting) in relation to the total muzzle energy (kinetic plus chemical, typical mix):

MK 108 (30x90RB): 860 kJ/kg
MK 103 (30x184B): 634 kJ/kg
MG 151/20 (MX) (20x82): 547 kJ/kg
MG 151/20 (20x82): 494 kJ/kg
Hispano II (20x110): 432 kJ/kg
MG-FF (20x80RB): 288 kJ/kg
MG 151 (15x96): 201 kJ/kg
,50 Browning M2 (12,7x99): 198 kJ/kg
MG 131 (13x64B): 180 kJ/kg
MG 17 (7,92x57): 147 kJ/kg
Browning ,303 (7,7x56R): 146 kJ/kg

So the Hispano ammunition is more than twice as effective per unit of weight than the 12.7 mm Browning ammunition, and the MG 151/20 ammunition about 2.5 times as effective.

The MG FF looks a bit inefficient in this comparison due to the inclusion of the weight of the drums, which means that it is not entirely comparable since belt-fed guns required ammunition boxes that were not considered in this comparison. However, leaving out the weight of the drums would make the MG FF look artificially good, so that's no solution either.

30 mm cannon further increase their weight efficiency, with the high-velocity MK 103 projectiles being three times as effective per unit of weight than the 12.7 mm Browning, and the MK 108 projectiles even four times as effective.

Regards,

Henning (HoHun)


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## Watanbe (Dec 15, 2008)

Glider said:


> For those who prefer the P38 the Whirlwind beats it into a cocked hat.



I dont like the P38 just its nose armaments. I love the Whirlwind its one of my favourite planes, its a pity it never got those merlins!


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## renrich (Dec 15, 2008)

Re the Tempest with four 20 MMs, the P51 also mounted 4 20MMs as did the F4U 1C. The throw weight of those models was 11.6 Lb/Sec. Interestingly, the TW of the P47 was 12.72 Lb/Sec and the TW of the cannon armed F6F was 12.16 Lb/Sec, both slightly more than the all cannon AC.


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## HoHun (Dec 15, 2008)

Hi Renrich,

>Re the Tempest with four 20 MMs, the P51 also mounted 4 20MMs as did the F4U 1C. The throw weight of those models was 11.6 Lb/Sec. Interestingly, the TW of the P47 was 12.72 Lb/Sec and the TW of the cannon armed F6F was 12.16 Lb/Sec, both slightly more than the all cannon AC.

Well, "throw weight" neglects the destructive capability of the projectiles, which obviously is considerably greater for explosive shells than for inert bullets. You've used an example from a maritime context, so you'll be aware of the impact shell guns had on naval tactics and technology - they were far more effective than the same weight of solid cast-iron cannonballs.

Here is an overview of the destructive capability in relation to projectile mass for a couple of aircraft guns:

MK 108 (30x90RB): 1524 kJ/kg projectile mass
MK 103 (30x184B): 1766 kJ/kg projectile mass
MG 151/20 (MX) (20x82): 1068 kJ/kg projectile mass
MG 151/20 (20x82): 1040 kJ/kg projectile mass
Hispano V (20x110): 791 kJ/kg projectile mass
Hispano II (20x110): 817 kJ/kg projectile mass
MG-FF (20x80RB): 959 kJ/kg projectile mass
12,7mm UB (12,7x108): 586 kJ/kg projectile mass
Berezin B-20 (20x99R): 518 kJ/kg projectile mass
20mm ShVAK (20x99R): 518 kJ/kg projectile mass
MG 151 (15x96): 590 kJ/kg projectile mass
MG 131 (13x64B): 396 kJ/kg projectile mass
,50 Browning M2 (12,7x99): 508 kJ/kg projectile mass
12,7mm Scotti (12,7x81SR): 352 kJ/kg projectile mass
Browning ,303 (7,7x56R): 415 kJ/kg projectile mass

For direct comparison:

Hispano II (20x110): 817 kJ/kg projectile mass <- F4U-1C battery
Hispano V (20x110): 791 kJ/kg projectile mass <- Tempest V battery
,50 Browning M2 (12,7x99): 508 kJ/kg projectile mass <- P-47D battery

So the 20 mm cannon offer about 50 % higher effectiveness than the 12.7 mm machine guns in relation to the projectile mass fired by each weapon type.

(By the way, are you sure of your throw weights? Using Tony's data, I get 6.24 kg/s for the Tempest and just 4.48 kg/s for the P-47, so I suspect there is an error in your data somewhere.)

Regards,

Henning (HoHun)


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## renrich (Dec 15, 2008)

No question that the TWs are not the best indicator of destructive power. In the case of 30 cals v 50cals they would be but the explosive projectiles make a big difference. Unless I mis copied the data I feel pretty confident of them. They come directly from my "bible," "America's One Hundred-Thousand," by Dean. I doubt there is a mistake there since the data was probably taken directly form USAAF and USN sources.My analogy of the CAs and CLs left out a factor which the RN felt was vital in their judgment. That factor was that they felt like the CLs would often engage at night or in bad weather where the ranges would have been shorter and the bigger punch of the 8 incher would not be as decisive. My purpose in posting in this thread(which I originated) is not to win an argument but rather to keep the discussion going and to post data which is thought provoking. Personally, I lean toward the armament of the Hellcat with the two cannon and four 50s. Unless I see data to contradict, I feel the 50 BMG round has the best ballistics of all commonly used weapons in WW2 AC from a rate of fire, flat trajectory and down range velocity point of view, which makes it easier to get hits with although not as destructive as the cannon and with a fire time of 26.7 seconds in the Hellcat those factors would give the pilot the best chance of getting hits on the opponent, particularly another fighter while the two 20 mm cannon with a fire time of 22.5 seconds in the Hellcat would give the pilot the additional destructive power to bring down a well armored AC or a lightly armored one with only a few hits. However, the P38 certainly, with all of it's guns concentrated and only one less cannon than the Hellcat certainly would be formidable. It's cannon fire time was only 15 seconds but the 50s had 33.3 seconds of fire time. Dean uses the following for rates of fire; 20 mm-10 rds/sec and 50BMG-15 Rds /sec. The TW of the P61 was almost 18 pounds/sec. 4-20mms and 4-50BMGs all concentrated. Would ruin your day to get in front of that.


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## HoHun (Dec 15, 2008)

Hi Renrich,

>No question that the TWs are not the best indicator of destructive power. In the case of 30 cals v 50cals they would be but the explosive projectiles make a big difference. 

I note you keep using it for the comparison of different calibres anyway.

>My purpose in posting in this thread(which I originated) is not to win an argument but rather to keep the discussion going and to post data which is thought provoking.

Baiting me to post stuff that you then proceed to disregard is just another way of trolling. Welcome to my ignore list ...

Kind regards,

Henning (HoHun)


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## SoD Stitch (Dec 15, 2008)

Any of the _Sturmbock_ Fw-190's would probably be the most destructive; hard to go wrong with two 13mm machine guns, two 20mm cannons, and two 30mm cannons.


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## claidemore (Dec 16, 2008)

On the subject of nose guns vs wing mounted guns:

I'm of the opinion that the 'single stream' of projectiles from nose mounted guns is not that big of an advantage given the technology of gunsights used during WWII. The odds of hitting a fast maneuvering target were just too great. I believe the mounting of guns in the nose or the wing of a particular aircraft tended to be more of a design consideration, rather than a gun 'effectiveness' issue. 

As Henning pointed out in an earlier post, the highest chance of hitting an airborne target from an airborne gun platform, was at the ranges where wing mounted guns were harmonized. The only place I see an advantage is at extremely close range where all guns could be brought to bear on an unsuspecting target. Anecdotal evidence suggests that most WWII pilots fired at much longer ranges, often at too long a range. 

With computerized gunsights a concentrated hail of fire is a definite asset, as seen during Korea when F86's were making extremely long range hits on Migs.

We also have to remember that wing mounted guns are generally only 10 to 15 feet apart, and are firing at a target that is 30x40 feet (average fighter), or greater. Most pilots aimed at the enemy plane, not at a specific part of the plane. 

WWII aerial gunnery is comparable to wing shooting with a shotgun, not precision shooting with a target rifle.

On a completely different subject, this thread encouraged me to do some reading about the P61, and apparently no P61s were lost to enemy action!


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## fly boy (Dec 16, 2008)

i'd go for the p-51 and p-47 because they both have at least six .50 cals and those are good in killing power, rate of fire and ammo


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## syscom3 (Dec 16, 2008)

Just a thought about mixing the cannons and MG's together on an aircraft ..... didnt the projectiles have different trajectories that made it near impossible to have all of them fired at once and hit what you thought you were aiming for?

Either you fire you MG's or your cannons, but not both (unless youre so close it didnt matter).


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## KrazyKraut (Dec 16, 2008)

claidemore said:


> I believe the mounting of guns in the nose or the wing of a particular aircraft tended to be more of a design consideration, rather than a gun 'effectiveness' issue.


Where's the difference? Nose armament was seen as more effective / efficient by some air forces. Thus they made it a requirement and subsequently it was incorporated in those designs. One leads to the other.



> As Henning pointed out in an earlier post, the highest chance of hitting an airborne target from an airborne gun platform, was at the ranges where wing mounted guns were harmonized. The only place I see an advantage is at extremely close range where all guns could be brought to bear on an unsuspecting target. Anecdotal evidence suggests that most WWII pilots fired at much longer ranges, often at too long a range.


 No. When not exactly at the point of convergence (harmonization), shots from a centerline gun deviate from the point of aim only on the y-axis, while those of a wing mounted gun deviate from that point on both y- and x-axis.

Contrary to what you wrote, a centerline gun is beneficial at all ranges, before or beyond harmonization range.

Overall it didn't matter that much because fighters with wing guns usually had a lot of them (except early P-51s). I like the statement that this kind of weaponry was effective but not efficient. There's something to it. Things would've probably been a bit different if they had to fight heavy bombers, but that's another story.


> Just a thought about mixing the cannons and MG's together on an aircraft ..... didnt the projectiles have different trajectories that made it near impossible to have all of them fired at once and hit what you thought you were aiming for?
> 
> Either you fire you MG's or your cannons, but not both (unless youre so close it didnt matter).


 In my opinion, for most combinations the difference is not bigger than the typical error a pilot would make anyway. As said by claidemore, a certain amount of spread is probably even beneficial. Up to convergence range, hit probability was apparently seen as sufficient, else you wouldn't see so many mixed gun platforms (basically all fighters except for early British and of course American single engined fighters). Even with the same type of guns there is some minor trajectory deviation between inner and outer guns.


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## HoHun (Dec 16, 2008)

Hi Claidemore,

>I'm of the opinion that the 'single stream' of projectiles from nose mounted guns is not that big of an advantage given the technology of gunsights used during WWII. The odds of hitting a fast maneuvering target were just too great. 

The problem with wing-mounted guns is that in most typical situations, the pattern extends horizontally while you need it to extend vertically. 

a) Imagine a shooter setting up a tracking shot by turning with a target aircraft ... both are rolled into the same turn, and the difficult thing to get right is the lead, which is controlled by the vertical displacement of the pipper above the target in the sight picture. What convergence/divergence gives you is a horizontal spread - but that's the dimension that easy to get right anyway.

b) Imagine a shooter setting up a snap shot by crossing the flight path of the target ... typically, that's done by tracking for a short moment and then pulling ahead and letting the nose fall back again immediately, firing a short burst while this happens so that the target flies through the burst. Just as in case a), shooter and target will have their wings in the same plane so that the difficult dimension is the vertical while the convergence/divergence is in the vertical.

c) Imagine a target crossing in front of the shooter from the left to the right so that a snap shot is possible without prior tracking. OK, here the horizontal pattern is helpful 

d) Imagine a target clearly beyond convergence range. This kind of long-range shooting is only feasible with a non-manoeuvring target, probably one trying to run at full power from a slower pursuer (for example a MiG running from an F-86, as described by Blese). The main problem is trajectory curvature there ... vertical dimension. The centreline-gun fighter can simply put the pipper on or above the target and fire away. The wing-gun fighter has to estimate the range and put the pipper on the wing, on the wing tip or even outside of the wing tip of the target, depending on the exact range. Even so, only half of the guns will hit. (If he aims right for the target, most of his fire will go above and below the wings if he's within about two times convergence range, or even miss the target entirely if he's yet farther away.)

e) Imagine a target in good shooting range. Whatever the situation, the centreline fighter can simply fire away without knowing the exact range. The wing-gun fighter still has to keep track of the range as getting too close is just as bad as being too far. Priller's "JG 26" has an example for a Luftwaffe pilot suddenly seeing tracers passing him closely on both sides of his fuselage, evidence of a P-47 attacking him from point blanc range (but failing to compensate for wing guns). USAAF pilots were aware of this effect as well - quoting Major Riemensnider (from "Combat Profile: Mustang" by Roger Freeman: 

"I had previously flown the twin-engined P-38 Lightning where the nose-mounted armament made for an ideal gun platform. Ranging wasn't the problem it was with the P-51 and other fighters which had wing-mounted armament where the fire converged. It out outfit the guns were adjusted for a point of convergence 300 yd ahead where, theoretically, they gave an approximately 8 x 10ft bullet pattern. In practice, because of the speed of closure, it was not easy to achieve that exact range when you hit the gun trigger. So there was a tendency for pilots to open fire at a target further off and hold a long burst as they closed. If you got in a correctly ranged burst, it was highly destructive."

Mölders summed it up concisely as "One cannon in the nose is as good as two in the wings". (Galland, when asked by Hitler what he preferred, pointed out "I'd rather have all three" - thus the Me 109 wing gondolas 

>Anecdotal evidence suggests that most WWII pilots fired at much longer ranges, often at too long a range. 

Well, the RAF evaluation showed that killing ranges were shorter than 366 m in 86 % of the cases, and this number is already based on half of the kills being achieved with computing gunsights. With standard sights, 92 % of the kills were achieve at 366 m and less. This would actually support your view by showing that case d) above is just an unimportant disadvantage 

An additional disadvantage of wing armament which you didn't mention is that wing guns also have a higher dispersion than centreline guns due to the flexiblity of the outer wings. This leads to a poorer concentration of fire and results in decreased effectiveness even beyond the pure convergence/divergence problems.

>On a completely different subject, this thread encouraged me to do some reading about the P61, and apparently no P61s were lost to enemy action!

One He 177 tail gunner claimed a P-61 shot down (though he misidentified it as a Lightning), but the P-61 actually managed to return home after putting out an engine fire caused by the tail gunner's hits in a steep dive. This dive of course created the illusion of a shoot down - what the gunner saw was a streak of fire going down rapidly, then disappearing at low altitude. I think I read about this several times, the first time in Jet + Prop which had full details on both the He 177 and the P-61 crews.

Regards,

Henning (HoHun)


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## HoHun (Dec 16, 2008)

Hi Syscom,

>Just a thought about mixing the cannons and MG's together on an aircraft ..... didnt the projectiles have different trajectories that made it near impossible to have all of them fired at once and hit what you thought you were aiming for?

>Either you fire you MG's or your cannons, but not both (unless youre so close it didnt matter).

No problem at all. The effective combat ranges were in fact so close that it didn't matter (closer than 400 m), and depending on the exact weapon type, the differences might in fact be smaller than the dispersion of a single weapon type at these ranges. Remember that the weapons were bore-sighted individually, so that the type with the more curved trajectory would be set to fire higher than the type with the flatter trajectory.

Even looking at the Me 109G-6/U4 with wing gondolas (nose MK 108, cowl MG 131, wing MG 151/20) has just 60 cm vertical difference between MK 108 and MG 151/20 at 400 m ... compare this to the 8 x 10 ft bullet pattern for the P-51 at 300 yards pointed out by Riemensnider, and you'll see it's hardly worth noting.

In fact, operational testing of the first Fw 190 aircraft showed that pilots preferred wing root cannon and cowl guns to be fired by the A button and the outer wing cannon by the B button over the factory configuration, which had the MGs on the A button and all cannon on the B button.

Unfortunately, it's not a perfect example as wing-root cannon were MG 151/20 and outer wing cannon MG FF/M, so there were actually three sets of trajectories involved  However, I can still point out that the preferred set-up was the one that gave one set of guns that were not affected by convergence issues, so it's a fair indication that these were important to the front-line pilots.

Regards,

Henning (HoHun)


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## renrich (Dec 16, 2008)

Sys brings up an interesting point which in a roundabout way I have been trying to get to and that is that the flight ballistics of the different projectiles might vary a lot. For instance, the A6M had two 20 mms with 60 rds of ammo each. Their rate of fire was around 5oo rds/min and had a muzzle velocity of 1968 fps. I don't have the figures for the two 30 cals in the nose but imagine they had a MV of around 2600-2800 fps. In other words they were kicking along at about 600 or 800 fps faster at the muzzle than the cannon rds. I don't know what the ballistic coeficient of the cannon rds were but suspect it was not as good as the MG rds. That means that the trajectory of the projectiles will be different, which can be compensated for but the flight time will be different which can't be compensated for. My math could be screwy but the cannon rds could perhaps arrive a full second later than the MG rds depending on the range. I have done a lot of shooting at animals and one can really tell the difference in a slow bullet like a 22 LR and a fast one like a 270 Win in the time it takes to get to a target. On an airplane that might be traveling 350 mph, that translates to 513 feet per second so if a cannon rd gets to the target a tenth of a second later then it might miss completely or if the guns are sighted in together and the cannon round hits the MG bullets are going to miss in front. This would be for a full deflection shot. I do know the Japanese used all guns at once at times but sometimes only the mgs until they got close and then triggered the cannon. I also know that many WW2 pilots opened fire at too long a range just as many of us do when hunting with shotguns. 300 yards is pretty much point blank range as far as trajectory is concerned with MG bullets. 300 yards is 900 ft so if the avg vel over 300 yds is 1800FPS the bullet get there in .5 seconds. If a cannon rd averages 1500 fps then it takes .6 second to get there. In a tenth of a second the target on a full deflection shot had traveled around 50 feet. Most fighters are not that long. Hmmmm!


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## HoHun (Dec 16, 2008)

Hi Krazykraut,

>Contrary to what you wrote, a centerline gun is beneficial at all ranges, before or beyond harmonization range.

Absolutely ... and even at harmonization range in a way, because the pilot has not to think about his range, freeing his mind for tactical thoughts  Of course, that's not quantifiable, but in a fast-moving dogfight, it's an important factor anyway.

Attach two graphs, showing the sight picture and pattern for a MK 108 nose cannon as mounted in the Me 109 and the 12.7 mm Browning M2 wing guns as mounted in the P-47 for ranges from 700 m (top) to 100 m (bottom) in 100 m steps. The target silhouette is approximately of P-47 size.

The pilot is considered to compensate for the trajectory drop. Note that this is hardly noticable for the M2 Browning, and only clearly evident for the MK 108 at long ranges. In fact, even the low-velocity MK 108 can perfectly well be used for "boresight" shots (where the pilot ignores trajectory drop and simply puts the pipper in the middle of the target) at ranges out to 500 m.

I think the graphs illustrate Major Riemensnider's point about the impact of the correct firing range when using wing guns quite nicely.

Regards,

Henning (HoHun)


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## kool kitty89 (Dec 17, 2008)

HoHun, an important point about guns of significantly different velocity. 
The trajectories may not be very different in the practical firing range, but time in flight will. 
Higher velocity projectiles (particularly those with a ballistic coeficient equal or grater than the low velocity projectile's) will get to the target much faster, and while the actual difference may be fairly small, in a tight turn (moving frame of refrence) the slower shells could go behind the target while the high velocity one hit. (the curved trajectory becomes greater due to the moving frame of refrence)


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## Glider (Dec 17, 2008)

I hae been having a think about this and have changed from the Tempest which probably had the heaviest firepower, to the Fiat G55 which I now think was the best armed fighter. There is a difference.

The reason is as follows.

The Fiat G55 had a 20mm and 2 x HMG in the nose giving it all the benefit of being a centralised weapon for accuracy and long range, plus of course the 20mm didn't have any problems with synchronisation. In addition the 2 x 20mm in the wings would be ideal for Heavy Bombers or if you have a good shot at a fighter.

What it also had, was a huge amount of ammo. The Central 20mm carried 380 rounds, so the pilot didn't have to be afraid of having a snap shot or firing at the longer ranges.
The wing guns carried 200 rounds per gun which is more than the average.
Put it together, and its a formidable package.


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## Juha (Dec 17, 2008)

Hohun

quote: ”a)… both are rolled into the same turn, and the difficult thing to get right is the lead, which is controlled by the vertical displacement of the pipper above the target in the sight picture.”

IMHO in fact the right lead in horizontal turning fight needs the skill to put the piper on right amount ahead of the target and to correct ballistic drop one needed to put the piper on the right amount above enemy’s projected flight path and when in bank other than 90 deg the wing armament gives some leverage in both directions.

In fact this is a question in which different air forces had different ideas; LW, VVS and Finns valued highly armament concentrated in nose, some others preferred wing armament. And in LW there were those Galland and Mölders schools. And I'm sure that there was also debates inside RAF and USAAF.

After the war nose armament became a norm, Sweden put sometimes cannon in the wings (Draken, Viggen), UK’s Meteor NFs and Javelin also had wing armament but they were AW fighters. How much the need of thin wing, but in deltas, dictated that or was it purely product of conclusion that nose armament was more effective, I don’t know. 

Glider
IMHO still Tempest and FW 190 from A-6 onwards were best. Tempest armament was more than enough against all aerial targets it met, be it Ju 188 or Me 262 or Bf 109. 4 * MG 151 should have been enough against fighters, medium bombers and Il-2s. Heavy bombers were a bit problem for average pilots but heavier armament would have made 190 more vulnerable to enemy fighters. So a good compromise. The two inner MG 151s allowes a tight pattern and MG 151 didn't suffer badly from syncronation


Juha


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## Glider (Dec 17, 2008)

Juha said:


> Hohun
> Glider
> IMHO still Tempest and FW 190 from A-6 onwards were best. Tempest armament was more than enough against all aerial targets it met, be it Ju 188 or Me 262 or Bf 109. 4 * MG 151 should have been enough against fighters, medium bombers and Il-2s. Heavy bombers were a bit problem for average pilots but heavier armament would have made 190 more vulnerable to enemy fighters. So a good compromise. The two inner MG 151s allowes a tight pattern and MG 151 didn't suffer badly from syncronation
> 
> ...



The Tempest I ruled out as being all wing mounted, the guns would have problems with long range shooting.
The 190 I seriously considered. You are of course correct in saying that the two inner 151's give a tight pattern and I don't doubt that the throw weight of those two guns was more than the single centerline weapon on the G55, even if the slightly better italian HMG's helped with the difference. However, what turned it for me was the ammount of ammunition that was carried. Nothing I know of comes close. 
I believe that the choice is between these two, leaving out the Jets of course.

The Whirlwind at first glance would be a contender with 4 x 20mm in the nose, but with only 60 rpg, I don't think so.


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## kool kitty89 (Dec 17, 2008)

HoHun, 
In your charts in post #65, they apear to be for guns set to converge at a single point. However the guns could also be "harmonized" to converge at varying ranges, giving higher dipursion but better hit probability and a larger convergence zone. (IMO a better congiguration than the single point, of course the broadness of the convergence zone is limited by the number of guns -obviously it could not be done with just 2x wing guns)

For example, with a six gun fighter, you could set the convergence for the guns to be at 250 yards, 300 yards, and 350 yards to give a good firing zone at a reasonable range. (although at very close range it will still be necessary to fire off to the side of the target, or skid back and forth so that the guns will be on target)

Here's a picture to represent what I was referring to:
The WWII Fighter Gun Debate: Ballistics


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## renrich (Dec 18, 2008)

KK, I have read that some Hellcat pilots had the guns synchronised exactly as you have written, Have see a photo where USN fighters were lined up on the fight deck with the tails jacked up firing at a target sled in the water. Since they appeared to be under way(this was early on and the planes were Wildcats and they were in a hurry) there must have been another ship towing the sled.


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## HoHun (Dec 18, 2008)

Hi Koolkitty,

>In your charts in post #65, they apear to be for guns set to converge at a single point. However the guns could also be "harmonized" to converge at varying ranges, giving higher dipursion but better hit probability and a larger convergence zone. 

This one distracted me a bit because it have never seen it in a firepower discussion before  I have not forgotten the other posts above, but I'll answer your point first because I was fascinated!

Attached you'll find my firepower comparison between P-38 with 4 x 12.7 mm machine guns (as before), and the P-47 with 8 x 12.7 mm machine guns set up to converge at 250 m (as before), and additionally between variations with a different convergence range for each of the four pairs of guns.

In short: Setting up different convergence ranges is not worth it. The reason is simply that you can't make more guns hit than before because they're still mounted unfavourably in the wings.

You can see that the characteristic hit power peak of the wing guns gets smaller (as you no doubt expected) with increasing difference between individual gun pair convergence ranges, and for the largest difference indicated in the diagram you can even see exactly four small peaks in the graph, each equivalent to the peak of one pair.

True, the zone of good hit power extends over a longer range, but at the same time the peak decreases so much in size that it finally drops below the nose gun hit power curve which is achieved with only half the number of guns!

The main gain of the multiple-range harmonization is at long range, but it's still markedly inferior to the nose-gun battery there, and as the area below the hit power curve stays (approximately) constant regardless of the choice of convergence ranges, the better long range hit power is paid for with poorer short range hit power - and the RAF statistics show that most kills were achieved at rather short range.

About the method for generating the new graphs: They are arithmetically derived from the original firepower graph which is scaled in power to 25% of the full battery (2 out of 8 guns - simple! , and scaled in range to simulate the different convergence ranges for each pair of guns. The values read from the four resulting individual graphs which are exactly of the original shape (though not dimesion) are then added up for each range on the range axis to arrive at the total firepower.

This is a deliberate simplification that does not take into account that the apparent target size at the scaled ranges would change. This underestimates target size at short range, and overestimates it at long range, exaggerated hit chances in the latter case. (You can see the effect of target size in the P-38 graph.) To err on the optimistic side, I have selected two longer convergence ranges and just one shorter convergence range so that multiple-range harmonization appears slightly more attractive than it actually is.

(Even the simplication was a bit complicated to capture in a diagram, but I think the result is well worth the effort 

Regards,

Henning (HoHun)


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## slaterat (Dec 18, 2008)

Hohun

I think what Kitty is refering to was called a box convergence, as opposed to a point convergence. This became more common with the introduction of the heavier armed fighters in the RAF such as The Hurricane IIc, the Typhoon and the Tempest. The guns would be aimed to hit a set area at a specific range. ie at 200 yds a 5 ft by 5ft target window would be evenly hit. This is one of the nice advantages of a 4 20mm cannon armament. The size of the box would be limited by the number of guns x the dispersion area of a single gun at a set range. 


Slaterat


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## HoHun (Dec 19, 2008)

Hi Slaterat,

>I think what Kitty is refering to was called a box convergence, as opposed to a point convergence. 

According to what I've read, the RAF's "box convergence" also had a deliberate vertical spread of the pattern, with some weapons firing high and some low. The example given was the Spitfire, which actually had the snigle port and the single starboard cannon adjusted differently.

However, with regard to horizontal harmonization, the box convergence has exactly the disadvantages I outlined above. Vertical spread does not increase the concentration of fire either, so hit power would drop even further if you'd introduce that. (Chances of achieving at least a few hits would obviously increase.)

Regards,

Henning (HoHun)


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## HoHun (Dec 19, 2008)

Hi Koolkitty,

>HoHun, an important point about guns of significantly different velocity. 
The trajectories may not be very different in the practical firing range, but time in flight will. 

>Higher velocity projectiles (particularly those with a ballistic coeficient equal or grater than the low velocity projectile's) will get to the target much faster, and while the actual difference may be fairly small, in a tight turn (moving frame of refrence) the slower shells could go behind the target while the high velocity one hit.

That's correct. However, unlike horizontal convergence/divergence, flight time difference increases the beaten zone along the vertical axis, which is a more useful spread when you are shooting at a tighly turning target.

(As attacks on tightly turning targets are only worthwhile from fairly short ranges, the impact of flight time difference is relatively small because the absolute projectile flight times are fairly short to behin with.)

Regards,

Henning (HoHun)


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## HoHun (Dec 19, 2008)

Hi Glider,

>I hae been having a think about this and have changed from the Tempest which probably had the heaviest firepower, to the Fiat G55 which I now think was the best armed fighter. There is a difference.

Interesting thought - I hadn't considered the Fiat fighter before.

>The Fiat G55 had a 20mm and 2 x HMG in the nose giving it all the benefit of being a centralised weapon for accuracy and long range, plus of course the 20mm didn't have any problems with synchronisation. In addition the 2 x 20mm in the wings would be ideal for Heavy Bombers or if you have a good shot at a fighter.
 
In terms of total firepower, the Fiat is in the top group, but actually a bit toward the bottom of the top group:

Me 262: 20,1 MW
Fw 190A-8/R2: 13 MW
Ta 152H: 7,6 MW
Fw 190A-8: 5,5 MW
Me 109K-4: 5,5 MW
Beaufighter Mk 21: 5,3 MW
Tempest: 4,9 MW
Fw 190A-4: 4,3 MW
Typhoon: 4,2 MW
Fiat G.55: 4,1 MW
Spitfire IXE: 2,7 MW

(Note the big gap to the Spitfire IXE - the "top group" is really clearly defined 

>What it also had, was a huge amount of ammo. The Central 20mm carried 380 rounds, so the pilot didn't have to be afraid of having a snap shot or firing at the longer ranges.

The total energy of the cannon rounds you describe comes down to 82.4 MJ. The Ta 152H had 67.2 MJ worth of cannon ammunition, combined with almost twice the firepower so that it was easier to knock down a target with a snap shot. Along with the all-centreline positioning of the Ta 152H's armament, this makes for a clearly superior battery in my opinion.

Regards,

Henning (HoHun)


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## Glider (Dec 19, 2008)

I am not suprised that the 262, 190A8-R2 and Ta152 are in a class of their own. That said, I am suprised that the G55 is so far behind the 190A8. The difference in only one 20mm 151, plus the G55 had a better HMG which should have reduced the gap as well as having a free firing 151 on the center line instead of the syncro guns on the 190.
I did expect the 190 to have a heavier throw weight but am suprised at the difference. The Ammunition point would still make me prefer the G55 though. 

The Beaufighter is more a strike plane than a fighter so I wouldn't have included it on that basis. Also the Ta152 I would ignore as being irrelevent. Only a handful (more a pinch) went into action and a Meteor would be a better aircraft.


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## HoHun (Dec 19, 2008)

Hi Glider,

>That said, I am suprised that the G55 is so far behind the 190A8. The difference in only one 20mm 151, plus the G55 had a better HMG which should have reduced the gap as well as having a free firing 151 on the center line instead of the syncro guns on the 190.

Well, heavy machine guns are not really powerful enough to make the difference you're expecting.

In detail:

MG 151/20

Fw 190A-8: 4 x 1.27 MW = 5.08 MW
Fiat G.55: 3 x 1.27 MW = 3.81 MW

Heavy machine guns

Fw 190A-8: 2 x 0.21 MW = 0.42 MW
Fiat G.55: 2 x 0.18 MW = 0.36 MW

Total:

Fw 190A-8: 5.08 MW + 0.42 MW = 5.50 MW
Fiat G.55: 3.81 MW + 0.36 MW = 4.17 MW

Hm, turns out that the Italian heavy machine guns actually are inferior to the MG 131. This is owed to the lower rate of fire of the Italian guns and the lower explosive content of the HE projectiles. (Both guns were considered to fire a 1:1 AP/HE mix.)

>The Ammunition point would still make me prefer the G55 though. 

Have you actually checked the ammunition count of the Fw 190A-8?

Fw 190A-8: 2 x 140 rounds + 2 x 250 rounds = 780 rounds
Fiat G.55: 2 x 200 rounds + 1 x 380 rounds = 780 rounds

Looks like less than a decisive advantage, to put it midly.

>Also the Ta152 I would ignore as being irrelevent. Only a handful (more a pinch) went into action and a Meteor would be a better aircraft.

Chauvinistic kneejerk. We're discussing armament technology, and the Ta 152H was clearly superior to the Meteor here, and battle-proven in WW2 air-to-air combat. If you mean to argue flight characterstics, performance and operational record, there are quite a few bad things to say about the WW2 Meteor, but that doesn't belong here.

Regards,

Henning (HoHun)


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## HoHun (Dec 19, 2008)

Hi Juha,

>IMHO in fact the right lead in horizontal turning fight needs the skill to put the piper on right amount ahead of the target and to correct ballistic drop one needed to put the piper on the right amount above enemy’s projected flight path and when in bank other than 90 deg the wing armament gives some leverage in both directions.

Hm, I don't think this vertical difference is a factor of meaningful magnitude.

Even in a tight turn at 90 degree bank, the apparent lateral drop of the projectile is about 8 cm after 1/8 s of flight, and 31 cm after 2/8 s of flight. After 3/8 s of flight and 70 cm of drop, the projectile has already reached the typical convergence range where the proposed advantage no longer exists. (And you're not likely to do any deflection shooting from a tight turn with 90 degree of bank at ranges beyond typical conversion range.)

As table:

Time - Drop - Lateral offset
1/8 s - 08 cm - 200 cm
2/8 s - 31 cm - 100 cm
3/8 s - 70 cm - 000 cm

(Average projectile speed ca. 800 m/s, P-47 gun setup.)

>In fact this is a question in which different air forces had different ideas; LW, VVS and Finns valued highly armament concentrated in nose, some others preferred wing armament. And in LW there were those Galland and Mölders schools. And I'm sure that there was also debates inside RAF and USAAF.

If you look at the available technology, the RAF and the USAAF had weapons that were not available with synchronization (the Hispano cannon) or too weak for a realistic nose gun battery and losing much of their rate of fire when synchronized (the 12.7 Browning M2).

The armament layouts we see are technology-driven, not demand-driven. Whenever the airframe layout allowed installation of nose guns, neither the RAF nor the USAAF decided for anything else but a centreline battery.

In fact, I've never seen any historical debate showing a preference for wing guns if nose guns were possible too. Galland's desire clearly was for the highest possible firepower, as evident both from his quote "I'd rather have all three" and from the equipment of his personally modified fighters, one having heavy machine guns on the nose, and the other adding wing guns while leaving the centreline armament in place.

>After the war nose armament became a norm, Sweden put sometimes cannon in the wings (Draken, Viggen), UK’s Meteor NFs and Javelin also had wing armament but they were AW fighters. 

Right now I can't think of any jet fighter with wing guns that were out on the wing and not in the root, and even that position obviously resulted from competition for space of the guns with the radar or, in the case of the Thunderflash, of the guns with the photographic equipment. I'm pretty sure that the common denominator of all these installations is "as close to the centreline as possible".

Regards,

Henning (HoHun)


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## Glider (Dec 19, 2008)

HoHun said:


> Hi Glider,
> 
> >Hm, turns out that the Italian heavy machine guns actually are inferior to the MG 131. This is owed to the lower rate of fire of the Italian guns and the lower explosive content of the HE projectiles. (Both guns were considered to fire a 1:1 AP/HE mix.)


Yep your right and I admit to not expecting that.


> Have you actually checked the ammunition count of the Fw 190A-8?
> 
> Fw 190A-8: 2 x 140 rounds + 2 x 250 rounds = 780 rounds
> Fiat G.55: 2 x 200 rounds + 1 x 380 rounds = 780 rounds
> ...


I don't disagree with this either, what I like about the G55 was how long it could continue firing. Its a personal preference.


> >Also the Ta152 I would ignore as being irrelevent. Only a handful (more a pinch) went into action and a Meteor would be a better aircraft.
> 
> Chauvinistic kneejerk. We're discussing armament technology, and the Ta 152H was clearly superior to the Meteor here, and battle-proven in WW2 air-to-air combat. If you mean to argue flight characterstics, performance and operational record, there are quite a few bad things to say about the WW2 Meteor, but that doesn't belong here.


Chauvanistic nothing - I always liked the 4 x 20 Hispano V grouped in the nose. Maximum firepower, very good long range shooting, good rate of fire. Certainly sufficient to deal with any likely enemy. However I didn't count it as it was in small numbers. 

The Mk103 is a fearsome weapon, but it does have a very slow ROF and its very heavy. If I was up against a B29 then its my weapon of choice, against a fighter thats trying to evade then the 4 x 20 Mk V would get my vote.

As an aside, I don't know how much ammo the Ta152 carried do you know?

Thanks again


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## renrich (Dec 19, 2008)

My source gives the TA152H-1 as one engine mounted 30 MM with 90 rds. and two 20 mm with 150 to 175 rds. These are firing through the propellor arc and will be synchronised. This armament is clearly designed to bring down bombers. An interesting parallel between a comparison of TA 152 and the P51D in ACM,(I don't know that they ever met), and the Mig 15 and F86. The TA152 had a 30 and two 20 mm cannon. The P51D had those six,(and sometime only four), 50 BMGs. The TA could outclimb the 51, had better high altitude performance and a higher service ceiling, ( some of these characteristics would apply to the FW190D9 also, climb and armament.) The Mig had the 30 mm and the 2- 20 mms and the advantage in climb and service ceiling over the F86 and the F86 had 6-nose mounted 50 BMGs, allegedly outmoded. From what I have read the P51D was at least equal to the FW190D9 and we will never know about the Ta. The F86 was clearly superior to the Mig as far as results. I have read that the 30 mm in the Mig was not at all effective against the Sabre, the 20s more so. The six fifties in the F86 seemed to get the job done. On the other hand, in the few encounters the straight wing F9F, with four 20 mms, had with Migs the F9F had the edge. Obviously a lot depended on pilot skills and other factors such as perhaps gunsights, although one Sabre driver is said to have said "stick a piece of gum on the windshield, stick the gum up his tailpipe, and let him have it ." What it all boils down to is that if you can't hit your target with your gun, it doesn't matter how big your gun is, which is the reason you hunt doves with seven and one halves or eights not fours.


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## Glider (Dec 19, 2008)

Thanks for the Information. I hadn't thought about it, but it is an interesting comparison with the F86/Mig 15.
Its only fair to admit that I belng to the F86 being underguned camp. It was OK against the Mig 15, but believe that it would have struggled against a B29 type of target. 
The 4 x Mk V 20mm I see as being a good middle ground.
Thanks again


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## HoHun (Dec 19, 2008)

Hi Glider,

>I don't disagree with this either, what I like about the G55 was how long it could continue firing. Its a personal preference.

That's just the muzzle loader effect - ammunition lasts long if firepower is low.

>Chauvanistic nothing 

Well ... of course none of the countless replies I got over the years which chose to ignore superior Luftwaffe technology at the respective most convenient moment have been motivated by anything but impartial and unbiased interest. Still, after a couple of thousand repetitions I seem to discern a certain pattern ...

>I always liked the 4 x 20 Hispano V grouped in the nose. Maximum firepower, very good long range shooting, good rate of fire. 

Not "maximum" in the context of WW2's best armed fighters, as there are quite a few that surpass it.

Me 262: 20,1 MW
Fw 190A-8/R2: 13 MW
Ta 152H: 7,6 MW
Fw 190A-8: 5,5 MW
Me 109K-4: 5,5 MW
Beaufighter Mk 21: 5,3 MW
Tempest: 4,9 MW
Fw 190A-4: 4,3 MW
Meteor: 4,2 MW
Typhoon: 4,2 MW
Fiat G.55: 4,1 MW

Long range shooting according to the RAF combat experience was a fringe phenomenon - 86% of the kills were achieved at ranges of 400 yards and less, and within those 400 yards again far more kills were achived at the shorter ranges than the longer ones.

That's the reason it pays off in air combat to increase firepower at the cost of long-range capability ... as the Ta 152H armament does, which yields almost twice the firepower of the Meteor's.

>However I didn't count it as it was in small numbers. 

"Zero" air-to-air kills?

>The Mk103 is a fearsome weapon, but it does have a very slow ROF and its very heavy.

The MK 103 is in fact lighter than the Hispano II if you consider comparable batteries:

1x MK 103 - 138 rpg, 20 s duration - 268 kg - 4,1 MW firepower - firepower per weight: 15,2 kW/kg
4x Hispano II - 204 rpg, 20 s duration - 401 kg - 4,2 MW firepower - firepower per weight: 10,6 kW/kg

So a single MK 103 equates the firepower of four Hispano II cannon, and for equal duration of fire comes out at just 67% of the total weight.

>If I was up against a B29 then its my weapon of choice, against a fighter thats trying to evade then the 4 x 20 Mk V would get my vote.

I think you are confusing the MK 108 and the MK 103. Are you aware that the Ta 152H used the fast firing, light MK 108 and the MK 103 is the larger high-velocity weapon with a greater muzzle velocity than the Hispano V?

>As an aside, I don't know how much ammo the Ta152 carried do you know?

The Ta 152H as the most lightly armed variant of the series carried 85 x 30 mm and 2 x 175 x 20 mm.

Regards,

Henning (HoHun)


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## Glider (Dec 19, 2008)

HoHun
Turn it down a bit, all I was doing was pointing out that I chose the G55 over the Meteor because of the small numbers involved, nothing more and nothing less. If that applied to all then the Ta152 would also fit that catergory.

If you want to compare the guns carried on the Ta152 with those on the Meteor then thats fine by me. Its my personal view that the 4 x 20mm Mk V in the nose of the Meteor, is a better all round system than that carried on the Ta 152.

I have said that the Mk103 is a fearsome weapon but it is heavy and does have a slow ROF for taking on agile fighters. No one is doubting the additional throw weight of the Ta152 but personally I don't think that is everything. The 2 x 20mm 151s are good but not exceptional for fighter work.

The 4 x 20mm Mk V in the nose has all the advantages of concentrated fire, longer range which can be very helpful when attacking bomber formations, a high rate of fire which would make it deadly against fighters, just a better all round set of weapons.

The comparison with the Mig 15 vs the F86 made by Rerich is a valid example of a twin weapon system which was lethal against bombers but not as good against fighters.


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## Juha (Dec 19, 2008)

Hello Glider
have been busy but on Tempest
IMHO (almost all of my limited shooting experience is from my 11 months compulsory military service, so I’m an amateur) the problems in long range shooting were not so significant. IIRC British pilots, who were not as indoctrinated to close range combat as Finns, usually harmonized their guns to 250-300yards, so the spread was broad as at 0y at 500-600y. IMHO ability to hit a fighter from 500-600y using WWII reflector sight was more in question of luck and “touch “/”instinct” than science. As res. vänr. (P/O) Puhakka, a future top ace of FAF, showed in 29 Jan 40 when he shot down a Soviet DB-3M bomber from 600-750m distance using one Oerlikon FF wing cannon (the one in other wing was jammed).

On the other hand, good fighter pilots could be very effective even with rather lightly armed fighters, as luutnantti (F/O) Sarvanto showed on 6 Jan 40. Armed with four .303 Brownings it was possible to shoot down 6 DB-3Ms in one engagement, even if DB-3M had protected fuel tanks and some armour protection for the dorsal gunner and for the pilot. And those were not claims but were verified by wreckages and in late 80s also by Soviet documents.

HoHun
we have argued on this earlier, so I have no need to repeat my points. Only one fact from our earlier discussion, the gravity drop for MG 151/20 was 1m at 280m from the muzzle of the barrel. Was that significant or not is a matter of opinion.

And there was at least one LW ace who told Finns that the layout of armament in Hurricane had its merits, he had personal experience on that, not a nice one.

Juha


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## HoHun (Dec 19, 2008)

Hi Glider,

>Turn it down a bit, all I was doing was pointing out that I chose the G55 over the Meteor because of the small numbers involved, nothing more and nothing less. 

Your words, direct quote:

"Also the Ta152 I would ignore as being irrelevent. Only a handful (more a pinch) went into action and a Meteor would be a better aircraft."

Do you seriously mean to suggest that the second sentence does not refer to the Ta 152 but to the G.55? No way I'm going to believe you ...

>I have said that the Mk103 is a fearsome weapon but it is heavy and does have a slow ROF for taking on agile fighters. No one is doubting the additional throw weight of the Ta152 but personally I don't think that is everything. The 2 x 20mm 151s are good but not exceptional for fighter work.

The Ta 152H does not have a MK 103. 

The MG 151/20 may be "good but not exceptional for fighter work" - hardly better than the Hispano V -, but the MK 108 is "exceptional for fighter work". It has single-hit kill potential, and "fighter work" is short-range combat. Look at the RAF war experience ... 86 % of all kills at 370 m and less.

>The 4 x 20mm Mk V in the nose has all the advantages of concentrated fire

The 2 x 20 mm and 1 x 30 mm in the nose of the Ta 152H has all the advantages of concentrated fire, too.

>longer range which can be very helpful when attacking bomber formations, 

This is an unproven claim. The Luftwaffe considered the hit rate to drop with the square of the firing range, and measured the danger to their fighters in exposure time, ranking their anti-bomber weapons by the time required to destroy an enemy bomber - not by the maximum distance at which it might be attacked. The MK 108 came out as second-best anti-bomber weapon, with the best being the MK 213C.

>a high rate of fire which would make it deadly against fighters, 

"Rate of fire" is not deadliness. Deadliness is the product of rate of fire and kill probability of the projectile. Thus, the firepower values I posted are direct indicators of the deadliness of the guns, regardless of the rate of fire. (Basic stochastics, really ...)

>The comparison with the Mig 15 vs the F86 made by Rerich is a valid example of a twin weapon system which was lethal against bombers but not as good against fighters.

One can't look at the strategical results of a confrontation between two air forces and then blame their guns for their results. The question is, "What did the Air Forces learn from the combat experience?" ... and this yields the exact opposite answer.

What really happened is that the F-86's armament was considered so seriously inadequate that a crash program was initiated to replace its weaponry with cannon (Project GUNVAL) even before the end of the war, practically ending the era of 12.7 mm machine guns as USAF fighter guns, while the Soviets considered the MiG-15's armament superior to that of the F-86 and continued to use the same battery in the MiG-17, with cannon of 23 mm calibre actually becoming the smallest calibre guns used in Soviet fighters after the Korean War.

Regards,

Henning (HoHun)


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## HoHun (Dec 19, 2008)

Hi Juha,

>we have argued on this earlier, so I have no need to repeat my points. 

Hm, that was a thread on snap shots vs. tracking shots. This one is slightly different, so don't hesitate to add stuff if you think it's of relevance 

>And there was at least one LW ace who told Finns that the layout of armament in Hurricane had its merits, he had personal experience on that, not a nice one.

I'd imagine being hit by gunfire was not a nice experience regardless of the exact type and setup of the guns  

(On a more serious note, the pilot hit by the Hurricane would not really have a way to compare his experience to what it would have been had he been hit by something else ...)

Regards,

Henning (HoHun)


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## Juha (Dec 19, 2008)

Hello HuHun
The German ace's opinion was that if the enemy had flown by 109F, the ace's plane had not taken any hits. Ie in some cases one was hit because of the spread of wing mounted armament sometimes one wasn't hit because of that

Juha


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## KrazyKraut (Dec 19, 2008)

renrich said:


> The Mig had the 30 mm and the 2- 20 mms and the advantage in climb and service ceiling over the F86 and the F86 had 6-nose mounted 50 BMGs, allegedly outmoded. From what I have read the P51D was at least equal to the FW190D9 and we will never know about the Ta. The F86 was clearly superior to the Mig as far as results. I have read that the 30 mm in the Mig was not at all effective against the Sabre, the 20s more so. The six fifties in the F86 seemed to get the job done.


There are a million factors involved so a valid conclusion on a single factor is impossible. Tactics, training, radar and of course gunsights. And we all know that the USAF was not at all pleased with the armament of the F86. Not to even mention we are talking about 1,75 times the combat speeds here, the whole scenario is pretty different.

The Ta 152 was not optimized for taking down bombers. Not more so than any other German fighter of that time. Its armament was supposed to give it a good all around performance against various types of planes, including bombers.


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## Glider (Dec 19, 2008)

HoHun said:


> Hi Glider,
> 
> Your words, direct quote:
> 
> ...


Henning, this started because I first nominated the Tempest then changed to the G55. I mentioned that I would have preferred the Meteor but left it out because of the small numbers and if that applied to them all then the Ta152 would not be in the list.
I made an error in the above posting and meant that the Meteor would in my view would be better armed. Apologies for the error 



> >I have said that the Mk103 is a fearsome weapon but it is heavy and does have a slow ROF for taking on agile fighters. No one is doubting the additional throw weight of the Ta152 but personally I don't think that is everything. The 2 x 20mm 151s are good but not exceptional for fighter work.
> 
> The Ta 152H does not have a MK 103.


I thought it did, simple mistake.



> The MG 151/20 may be "good but not exceptional for fighter work" - hardly better than the Hispano V -, but the MK 108 is "exceptional for fighter work". It has single-hit kill potential, and "fighter work" is short-range combat. Look at the RAF war experience ... 86 % of all kills at 370 m and less.


True but they never went up aganist massed bombers



> >The 4 x 20mm Mk V in the nose has all the advantages of concentrated fire
> 
> The 2 x 20 mm and 1 x 30 mm in the nose of the Ta 152H has all the advantages of concentrated fire, too.


True



> >longer range which can be very helpful when attacking bomber formations,
> 
> This is an unproven claim. The Luftwaffe considered the hit rate to drop with the square of the firing range, and measured the danger to their fighters in exposure time, ranking their anti-bomber weapons by the time required to destroy an enemy bomber - not by the maximum distance at which it might be attacked. The MK 108 came out as second-best anti-bomber weapon, with the best being the MK 213C.


No doubt true, but the Mk108 being the most effective bomber destroyer has a very low MV making it unsuitable for long range fire. By getting close they were exposed to the bombers fire.
Also is it possible that the high success rate against bombers was helpd by the guns use in nightfighters?



> >a high rate of fire which would make it deadly against fighters,
> 
> "Rate of fire" is not deadliness. Deadliness is the product of rate of fire and kill probability of the projectile. Thus, the firepower values I posted are direct indicators of the deadliness of the guns, regardless of the rate of fire. (Basic stochastics, really ...)


Rate of fire has a direct relationship on the ability to hit the target. The shell can be as deadly as it want if it cannot hit the target its pretty useless.
Can I nominate the Mollins 6pd on the Mossie as the best armed fighter? They did shoot down a Ju88 with it in the one attack it was used in, giving it a 100% hit rate.  



> >The comparison with the Mig 15 vs the F86 made by Rerich is a valid example of a twin weapon system which was lethal against bombers but not as good against fighters.
> 
> One can't look at the strategical results of a confrontation between two air forces and then blame their guns for their results. The question is, "What did the Air Forces learn from the combat experience?" ... and this yields the exact opposite answer.
> 
> What really happened is that the F-86's armament was considered so seriously inadequate that a crash program was initiated to replace its weaponry with cannon (Project GUNVAL) even before the end of the war, practically ending the era of 12.7 mm machine guns as USAF fighter guns, while the Soviets considered the MiG-15's armament superior to that of the F-86 and continued to use the same battery in the MiG-17, with cannon of 23 mm calibre actually becoming the smallest calibre guns used in Soviet fighters after the Korean War.



As it happens I agree that the important thing is what did each air force learn from the battles.
The USAF
They learnt that the 0.5 wasn't sufficient and went to *The 20mm*, please note my reply to Renrich.
The Soviet Airforce
The first fighter designed after Korea was the Mig 19 which went to *3 x 30mm.*. The Mig 17 was designed before Korea.



Regards,


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## Glider (Dec 19, 2008)

HoHun
Can I ask how you calculate your numbers for effectiveness. Antony Williams site which I am sure you know, gives differing numbers.

His numbers would give the Ta152 and Tempest very similar stats.


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## KrazyKraut (Dec 19, 2008)

The MiG-19 started with the same NR-23 that was used in Korea.


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## Glider (Dec 19, 2008)

I wasn't aware of that but the important thing for the exchange is that they didn't carry the 37mm.
Thanks for the info


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## HoHun (Dec 19, 2008)

Hi Glider,

>I made an error in the above posting and meant that the Meteor would in my view would be better armed. Apologies for the error

Aw, OK - let's forget it.

>No doubt true, but the Mk108 being the most effective bomber destroyer has a very low MV making it unsuitable for long range fire. 

Not really, it just required the pilot to apply extra elevation for long range fire. That would have decreased accuracy with a fixed sight, but you might have seen the comparison between MK 108 and high-velocity MK 103 which I posted recently in another thread on this board that shows that with the EZ 42 calculating sight, the MK 108 looked pretty good even at long ranges.

>By getting close they were exposed to the bombers fire.

The situation is symmetrical - fighters and bombers hit each other better at closer range, regardless of the actual distance. Only a very long-ranged weapon such as the 50 mm cannon tried on the Me 410 could hope to outrange the bomber weapons, and that approach had problems of its own.

>Also is it possible that the high success rate against bombers was helpd by the guns use in nightfighters?

The Luftwaffe ranking I mentioned was based on the weapons' performance parameters, so statistical fluctuations did not affect it. The two most highly prioritized parameters were duration of the burst necessary to kill a four-engined bomber, and the weight of the battery.

>Rate of fire has a direct relationship on the ability to hit the target. The shell can be as deadly as it want if it cannot hit the target its pretty useless.

If you have a 10% hit chance, 10% of the projectile will hit the target no matter what the rate of fire is. It doesn't matter if you fire 1000, hit with 100 or fire 10 and hit with 1 - what matters is the probability of kill per projectile.

If the 1000 you fired in the first case have a Pk of 0.2% each, and the 10 you fired in the second case have a Pk of 50% each, your chances for a kill are 20% in the first case and 50% in the second case.

Rate of fire only determines how long all of that takes, not how likely a kill is.

>The Mig 17 was designed before Korea.

Its armament was not changed after Korea though - just as I said, the Soviets continued to use the MiG-15's battery in the MiG-17. 

>The first fighter designed after Korea was the Mig 19 which went to 3 x 30mm.

Soviet fighters employed a greater variety of fighter guns than the US fighters, but 23 mm remained a common Soviet fighter gun calibre long after the Korean war, being used for example by the MiG-21 and MiG-23.

Regards,

Henning (HoHun)


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## HoHun (Dec 19, 2008)

Hi Glider,

>Can I ask how you calculate your numbers for effectiveness. Antony Williams site which I am sure you know, gives differing numbers.

I have pointed out my method above, and you'll even find it on Tony's site as well as he added it to his effectiveness page after we discussed the disadvantages of his "rule of thumb" approach on another forum.

>His numbers would give the Ta152 and Tempest very similar stats.

The disadvantage of his rule of thumb approach is that it underestimates low-velocity, high-explosive shells like the MK 108's, so this fits into the picture.

Regards,

Henning (HoHun)


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## Gnomey (Dec 19, 2008)

......


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## renrich (Dec 19, 2008)

Glider, If you recall I did bring up the experience( very limited) of the Navy jets with 4-20 mms against Migs and I believe that all the USN fighters except a few manufactured during WW2, in Korea, had gone to the 20 mms. I will repeat that I have read that the Mig's 30 mm was not thought to be very effective against fighters because of low ROF and low velocity. The factor which played a big role in forcing the retirement of the 50 BMG as a primary weapon in ACM was that jet aircraft did not have as many vulnerable parts and areas as piston AC have, so hits by a kinetic energy projectile like the 50 BMG were not nearly as likely to be productive. The 50 BMG in WW2 was a decidedly effective weapon although certainly not as effective as the various cannon rds on a rd for rd basis. Because of it's long range, flat trajectory and high velocity and high rate of fire if it were well aimed a lot of hits could be obtained and the bullets could pierce light armor plate, engine blocks and almost all of the structure of an AC. I have fired a 50 BMG at trucks and personnel carriers on the range and it is amazing what those bullets will do. Having said that the US 20 mms were also effective once teething problems were solved. Compare the following: 50 BMG weight-70 pounds, ROF-800 to 900 RPM, muzzle velocity- 2550 to 2840 fps, max. effective range-900 yards. 20 mm weight- 129 pounds, ROF-600 RPM, muzzle velocity-2920 FPS, max effective range-2400 yards. The factors I am unaware of are the ballistic coefficient of the 20 mm projectile which have a big effect on trajectory and flight time, the recoil effect and of course the amount of ammo carried. The fact that the A6M early on only carried 60 rounds per gun of cannon ammo had a very deletorius impact on the Zero effectiveness because of it's puny nose mounted armament. The low number of cannon rounds may have played a major role in the Midway debacle causing the IJN flight decks to be tied up by Zeros landing and rearming so that the second strike could not be launched before the US dive bombers got their licks in. As you can see the US 20 mm weighed considerably more than the 50 BMG and if four were carried in the wings, there would be a considerable wight gain over six fifties and the ammo weighed more also. Recoil forces must have been considerably more for the 20s. All these factors would have more effect on the lighter fighters versus the heavy and robust ones. Taking all this into account and discounting AC performance it seems likely the best armed fighter against another fighter would be the P38 with 150 rounds of 20mm cannon ammo and 500 rounds per gun for the fifties, all mounted in the nose with no synchronisation issues and with no convergence issues. On the other hand, against bombers, the P61 with four 20mms and four 50 BMGs would seem to be the winner, for many of the same reasons as the P38.


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## kool kitty89 (Dec 19, 2008)

HoHun, while I completely agree on the "muzzel loader effect" (the only advantage would be with pilots, mainly rookies, that tend to fire long burst and run their ammo out too quickly on low probability shots) you must agree that total ammo power is a seperate issue.

You said:


> The total energy of the cannon rounds you describe comes down to 82.4 MJ. The Ta 152H had 67.2 MJ worth of cannon ammunition



Which clearly shows that the G.55 had a higher total ammo power, granted at a lower fire power.

Also note the Re.2005 has a similar armament. (though different ammo load, with 350 rph for the 12.7mm's, 200 rpg for the wing cannon, and 150 rpg for the engine cannon) And according to wikipedia's figures, the G.55 had 300 rph 12.7mm, 200 rpg for the wing 20mm's, and 250 rpg for the nose cannon.


The ammo load for the Ta 152's wing root 20mm's seems unnecessarily low given that the Fw 190 had 250 rpg for these guns.

I also beleive the Ta 152H was intended (high altitude optimized) for fighter vs fighter combat, not specifically for bomber interception. If the latter had meen the case, a heavier armament would be likely be fitted. (like outer wing MK 108's)


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## Glider (Dec 19, 2008)

HoHun said:


> Hi Glider,
> 
> >No doubt true, but the Mk108 being the most effective bomber destroyer has a very low MV making it unsuitable for long range fire.
> 
> Not really, it just required the pilot to apply extra elevation for long range fire. That would have decreased accuracy with a fixed sight, but you might have seen the comparison between MK 108 and high-velocity MK 103 which I posted recently in another thread on this board that shows that with the EZ 42 calculating sight, the MK 108 looked pretty good even at long ranges.


Again I don't disagree but your getting close to the core of my point. If you allow for the ballistic drop of the Mk108, then the 20mm are going to miss. RAF aircraft also had sophisticated sights and they would be hitting with all their 20mm.



> >By getting close they were exposed to the bombers fire.
> 
> The situation is symmetrical - fighters and bombers hit each other better at closer range, regardless of the actual distance. Only a very long-ranged weapon such as the 50 mm cannon tried on the Me 410 could hope to outrange the bomber weapons, and that approach had problems of its own.


Again true but to a degree, the fixed gun is more accurate than the turret and the HMG loses more of its effectiveness at longer ranges. So by getting close you lose a lot of the advantages of the fixed wing fighter. 



> If you have a 10% hit chance, 10% of the projectile will hit the target no matter what the rate of fire is. It doesn't matter if you fire 1000, hit with 100 or fire 10 and hit with 1 - what matters is the probability of kill per projectile.
> 
> If the 1000 you fired in the first case have a Pk of 0.2% each, and the 10 you fired in the second case have a Pk of 50% each, your chances for a kill are 20% in the first case and 50% in the second case.
> 
> Rate of fire only determines how long all of that takes, not how likely a kill is.


Again I agree to a degree. The holy Grail is a gun with a high ROF and good ballistics, combined with a shell that give a good PK.
The Mk108 has a high ROF, Poor Ballistics and a High PK which means getting close.
The 20mm MkV has a High ROF, good ballistics and for a 20mm a good PK, which is assisted by having four of them. As mentioned a number of times I believe this is a more flexible arrangement. 



> >The Mig 17 was designed before Korea.
> 
> Its armament was not changed after Korea though - just as I said, the Soviets continued to use the MiG-15's battery in the MiG-17.


Neither were the weapons carried in the USAF F86. However the one that was designed post Korea for Australia had 2 x 30mm Aden.



> >The first fighter designed after Korea was the Mig 19 which went to 3 x 30mm.
> 
> Soviet fighters employed a greater variety of fighter guns than the US fighters, but 23 mm remained a common Soviet fighter gun calibre long after the Korean war, being used for example by the MiG-21 and MiG-23.


Again true but the point was that the first Soviet fighter produced after Korea went to a single weapon, away from a split 37mm/23mm payload. They had learnt the lesson. 
I think I am correct in saying that no other fighter post war had a mixed payload be it 37mm/23mm or 30mm/20mm.


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## kool kitty89 (Dec 20, 2008)

Renrich, note the MiG-15 carried the 37mm N-37 and 2x 23mm NS-23's (later replace with higher RoF NR-23's).

The 37 mm weapon was heavy and fairly slow firing in fact the standard 37mm HE shell only carried ~60% the explosive content of the much smaller 30 mm Mine shells of WWII. (granted there would be more shrapnel) The 23 mm's were medium velocity with decent rates of fire.


On the F-86, there were some variants fitted with 4x 20mm M39 revolver cannon. (including some F-86E's in trials in Korea) The F-86H had this as the Main armament. (as did the F-86K, though that was not a "normal" Sabre, but an all weather interceptor like the F-86D)

IMO the USAF should have followed the USN/USMC with the use of the M3 Hispano (in batteries of 4 in the nose of their F2H and F9F), and later the electric primed M24 with the USAF and then the M39. (though the Navy chose the somewhat problematic Colt Mk.12 cannon)


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## kool kitty89 (Dec 20, 2008)

Glider,
On the MK 108's range, HoHun showed in his graph that out to 500m the trajectory is reasonable. (should be somewhat better with the streamlined Minengeschoss Type N -Ausf C L-spur- the tracer element would also improve the ballistic qualities, while the high sectional density will give good speed retention -a property of corse shared with the standard blunt shell)

However the low velocity (granted with relatively good speed retention) will mean a fairly long time in flight, will make it somewhat harder to hit with. (and requiring greater lead in deflection shots as I mentioned previously)




HoHun said:


> Hi Glider,
> 
> >Can I ask how you calculate your numbers for effectiveness. Antony Williams site which I am sure you know, gives differing numbers.
> 
> ...



I tend to disagree.
While Tony's approach may seem somewhat arbitrary at first there is a good deal of sense behid it. And conversely, while it may seem a more imperical approach to use the kinetic energy values and add the chemical energy values on top of this for HE/I shells; the latter is IMO somewhat arbitrary as the effect of chemical and kinetic damage is not directly quantifiable in this manner not to mention the difference of HE chemical energy and Incendiary chemical energy. (not to mention different HE/I compositions, and if a pure white phosphorus filler is used there will technically be no chemical energy content at all in less you include atmospheric oxygen)

Firstly, when looking at solid ball/AP/SAP projectiles alone, using Muzzel energy is a rather poor choice as it thend to exaggerate the destructiveness of high velocity rounds compared to lower velocity rounds. Momentum (mass x velocity) tends to give much more realistic figures. 

Tony gives a explaination of the choice of his system in the article: 
WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

and there's this highlighting the momentum choice:


> For all of these reasons muzzle energy (one half of the projectile weight multiplied by the square of the velocity) has not been used to calculate kinetic damage as this would overstate the importance of velocity. Instead, momentum (projectile weight multiplied by muzzle velocity) was used as an estimate of the kinetic damage inflicted by the projectile. It might be argued that even this overstates the importance of velocity in the case of HE shells, as noted above, but the effect of velocity in improving hit probability is one measure of effectiveness which needs acknowledging, so it is given equal weighting with projectile weight.





> The relationship between the effectiveness of HE and incendiary material is difficult to assess. Bearing in mind that *fire was the big plane-killer*, there appears to be *no reason to rate HE as more important, so they have been treated as equal*.



Using chemical energy would tend to make HE more destructive than incendiary material. (a pyrotechnic mixture, in the case of the the "De Wilde" or Dixon- as well as the derived US incendiaries used a 50/50 mixture of Barium Nitrite and powdered aluminum/magnesium alloy rather like some types of flash powder used in pyrotechics -and these rouds did give quite a flash on impact)

And in particular guns of 13 mm or smaller caliber explosive rounds tended to be rather ineffective (probably not worth adding a delay fuze) despite it being used by both the Germans and Italians (on the .5" Vickers Semi-rimmed export) and thus by the IJA who used the same Italian type ammo. (the 13.2 mm FN Browning -firing the 13.2x99 Hotchkiss round -identical to the BMG save the caliber- offered HE ammunition as well, a did the Russians in the large projectiles of their 12.7x108mm amuntion though I don't know if either of these bothered with Fuzing)
The Japanese also used 7.7mm unfuzed HE rounds.

In any case, incendiary rounds tended to be more effective in such small calibers. (with 15mm/.60 cal weapons in kind of a gray area in terms of HE shell effectiveness, being just large enough to make the addition of a Fuze worthwhile particularly if a thin walled "mine shell" type projectile had been developed)


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## KrazyKraut (Dec 20, 2008)

kool kitty89 said:


> I tend to disagree.
> While Tony's approach may seem somewhat arbitrary at first there is a good deal of sense behid it. And conversely, while it may seem a more imperical approach to use the kinetic energy values and add the chemical energy values on top of this for HE/I shells; the latter is IMO somewhat arbitrary as the effect of chemical and kinetic damage is not directly quantifiable in this manner not to mention the difference of HE chemical energy and Incendiary chemical energy. (not to mention different HE/I compositions, and if a pure white phosphorus filler is used there will technically be no chemical energy content at all in less you include atmospheric oxygen)


The problem I have with William's approach is this:


> For projectiles with a chemical content, we increase this by the weight fraction of explosive or incendiary material, times ten. This chosen ratio is based on a study of many practical examples of gun and ammunition testing,


I would really like to know the study he mentions, but there is no link or source what-so-ever. What guns were studied, what calibre, what period etc... For example an educated guess tells me a study on modern guns will give a much more pronounced energy advantage for "chemical guns", as modern chemical agents tend to be more effective. As it stands his study is nicely written and probably gives acceptable relative outcomes, but the formula above looks largely arbitrary to me.


koolkitty said:


> And in particular guns of 13 mm or smaller caliber explosive rounds tended to be rather ineffective.
> 
> In any case, incendiary rounds tended to be more effective in such small calibers.


What do you base this on?


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## kool kitty89 (Dec 20, 2008)

I also would be interested to see what tests that ratio is based on. However it does corespond fairly well to the USN comparison of the Hispano to the .50 M2. (3x as effective at close-medium range, in fact Tony's figures are even more in favor of the cannon, the all-energy figures are significantly higher still)

On the HE machine gun rounds, there are a few reasons behind that statement (besides the "20 mm was determined to be the smallest caliber for a shell with worthwhile explosive capacity" statment -which is obviously debatable), The MG 131 HE round carried only 3.5% filler (1.2g) and the Italian-Vickers 12.7 mm even less at 2.2% (.73g) while the .50 BMG and .50 Vickers carry ~5% as pure incendiary rounds. ("de wild" derived) 

Things may be different for the somewhat larger projectiles of the 13.2x99 Hotchkiss and 12.7x108 Soviet amunition, but I'm not sure. (both offered HE ammo and the 12.7x108's API round carried 4.2% incendiary compared to only 2% for the .50 BMG's API)

And if it was possible to make an effective "mine shell" in such calibers it may have been worthwhile as well. (though pure incendiary may have still been more effective here)


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## HoHun (Dec 20, 2008)

Hi Koolkitty,

>Which clearly shows that the G.55 had a higher total ammo power, granted at a lower fire power.

That was a comparson G.55 vs. Ta 152H, the other was a comparison G.55 vs. Fw 190A-8 (which have, as I pointed out, the exact same number of 20 mm rounds).

>And according to wikipedia's figures, the G.55 had 300 rph 12.7mm, 200 rpg for the wing 20mm's, and 250 rpg for the nose cannon.

Oh, Wikipedia ...

>I also beleive the Ta 152H was intended (high altitude optimized) for fighter vs fighter combat, not specifically for bomber interception. If the latter had meen the case, a heavier armament would be likely be fitted.

Quite right. The Ta 152C would have two additional MG 151/20 cowl guns, and two outer wing MK 108 were possible too. It was even planned to use an engine MK 103 and to allow mounting of MK 103 gondola (instead of the outer wing MK 108). I don't think there was ever an aircraft such equipped, though.

Regards,

Henning (HoHun)


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## HoHun (Dec 20, 2008)

Hi Glider,

>If you allow for the ballistic drop of the Mk108, then the 20mm are going to miss. 

Oh well, you talked about the 30 mm being unsuitable for long range fire, which is not true.

>RAF aircraft also had sophisticated sights and they would be hitting with all their 20mm.

Yes, and in the case of the Meteor, with 4.2 MW combined firepower. Now the Ta 152H's single 30 mm offers 5 MW firepower, so when you simply cut out the 20 mm, the Ta 152H is still superior. 

(And even more than these muzzle power figures indicate - at long range, the kinetic energy has been considerably reduced by drag, while the chemical content is just as powerful as it was at the muzzle.)

>Again true but to a degree, the fixed gun is more accurate than the turret and the HMG loses more of its effectiveness at longer ranges. So by getting close you lose a lot of the advantages of the fixed wing fighter. 

The determining factor is the required mission effectiveness ratio for the fighter - even assuming the exchange ratio were more favourable at extreme ranges, the total number of downed aircraft would be down. In the Luftwaffe experience, effectiveness dropped with 1/r^2, so if you're out at three times the range, you get only 1/9 of the kills.

>As mentioned a number of times I believe this is a more flexible arrangement. 

Now there is an adjective that means everything and nothing.

>>Its armament was not changed after Korea though - just as I said, the Soviets continued to use the MiG-15's battery in the MiG-17.

>Neither were the weapons carried in the USAF F86.

Whom are you trying to fool? The weapons carried in the USAF F-86 were changed in Korea already because of their inadequacy, and there were quite a number of 20-mm-armed F-86 variants produced afterwards.

That the USAF considered the 12.7 mm guns woefully lacking in the light of their Korean experience is beyond doubt, and to me it looks as if you're trying to throw up a smokescreen here.

>Again true but the point was that the first Soviet fighter produced after Korea went to a single weapon, away from a split 37mm/23mm payload. They had learnt the lesson. 

The MiG-17 was the first Soviet fighter produced after Korea, and it had the combined armament for its entire service life, with the exception of radar-equipped aircraft which had the 37 mm cannon replaced by another 23 mm cannon to compensate for the additional weight of the radar and associated equipement.

If the mixed armament would have been considered a mistake, the 37 mm cannon would have been replaced by a 23 mm cannon on all aircraft in just the same manner, which didn't happen, so you have no point.

And to equate the mounting of a much more powerful battery in the MiG-15's successor's successor aircraft to the ripping out and replacing of the F-86's recognizedly inadequate armament in the framework of a purposeful project while the war was still going on takes you half the way to my ignore list already.

I see a pattern there, Glider - play fair, or don't play at all.

Regards,

Henning (HoHun)


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## HoHun (Dec 20, 2008)

Hi Kitty,

>While Tony's approach may seem somewhat arbitrary at first there is a good deal of sense behid it. 

It doesn't appear "somewhat arbitrary", it appears completely wrong. There is no reason for linking chemical content and muzzle velocity I could see, and I note you didn't provide any either.

>Tony gives a explaination of the choice of his system in the article: 
WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

You can assume I'm familiar with that as I criticized it when it came out, leading to Tony's addition. If there is anything you consider important, it would help if you'd explain it here because I still don't follow Tony's original explanation.

>and there's this highlighting the momentum choice:

Which makes claims, but gives no physical reason.

>fire was the big plane-killer

Unproven, probably resulting from a misunderstanding of the findings of a single report. (If fire was witnessed during the destruction of an aircraft. that doesn't mean that fire was the cause of the destruction - it could just as easily have been the result.)

>And in particular guns of 13 mm or smaller caliber explosive rounds tended to be rather ineffective [etc.]

Right - and that ineffectiveness is clearly evident in the energy figures, too.

Regards,

Henning (HoHun)


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## HoHun (Dec 20, 2008)

Hi Koolkitty,

>I also would be interested to see what tests that ratio is based on. However it does corespond fairly well to the USN comparison of the Hispano to the .50 M2. (3x as effective at close-medium range, in fact Tony's figures are even more in favor of the cannon, the all-energy figures are significantly higher still)

Well, I guess the question on what the US Navy based that conclusion on is just as interesting. 

The Luftwaffe compared the MG 151 in the 15 mm variant (which is pretty exactly twice as powerful as the 12.7 mm Browning) to the MG 151/20 cannon, and found the 20 mm cannon to be 3.25 times as effective. (This agrees well the energy-based analysis.)

Regards,

Henning (HoHun)


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## drgondog (Dec 20, 2008)

lesofprimus said:


> Real interesting stuff here fellas.... Surprised Drgondog aint in this...
> 
> If we can guys, lets keep this in the boundry of single engined fighters, and those utilized for air to air combat...



Dan - it just seems pretty straightforward that the 262, Fw 190A8, He 219, P-61 and F7F were the heaviest armed figters - and only one was a single engine fighter. Only the A8 had to depend on synchronization of any kind - all the rest push one 'solid tube' of very heavy firepower out of the nose.

And to think that one A-10 exceeds them all.


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## Glider (Dec 20, 2008)

I admit to having been doing some thinking and have some doubts about the statements being made.

For Example
The 30mm Mk108 I do not see as being acurate up to 500m and then suddenly dropping off. Its a heavy shell with a low MV. Gravity will take over and the shell drop. The statement earlier in the thread that you can keep the pipper on the target up to 500m I frankly disbelieve. 

There are two factors in external ballistics, Muzzle Velocity and Ballistic Co efficient, with the MK108 is well below average on MV.
The Ballistic Coefficient of the 30mm will tend to be slightly better than a 20mm but nothing like the difference between the different MV.


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## Glider (Dec 20, 2008)

HoHun said:


> Hi Glider,
> 
> >If you allow for the ballistic drop of the Mk108, then the 20mm are going to miss.
> 
> Oh well, you talked about the 30 mm being unsuitable for long range fire, which is not true.


I believe that it is unsuitable.



> >RAF aircraft also had sophisticated sights and they would be hitting with all their 20mm.
> 
> Yes, and in the case of the Meteor, with 4.2 MW combined firepower. Now the Ta 152H's single 30 mm offers 5 MW firepower, so when you simply cut out the 20 mm, the Ta 152H is still superior.


Can I ask how you calculate the 4.2 MW. I mention this as you give the Tempest a higher power when they are the same guns.


> (And even more than these muzzle power figures indicate - at long range, the kinetic energy has been considerably reduced by drag, while the chemical content is just as powerful as it was at the muzzle.)


You are of course correct but Kinetic Energy is less important in a cannon shell as they can penetrate almost any armour carried on an aircraft. The 20mm Hispano could penetrate 20mm at 400m, the punch is in the explosive content so any drop in Kinetic energy is of little consequence.


> >Again true but to a degree, the fixed gun is more accurate than the turret and the HMG loses more of its effectiveness at longer ranges. So by getting close you lose a lot of the advantages of the fixed wing fighter.
> 
> The determining factor is the required mission effectiveness ratio for the fighter - even assuming the exchange ratio were more favourable at extreme ranges, the total number of downed aircraft would be down. In the Luftwaffe experience, effectiveness dropped with 1/r^2, so if you're out at three times the range, you get only 1/9 of the kills.


Using low MV weapons that is probably true but to apply it to longer ranged weapons is an unproven fact



> >Again true but the point was that the first Soviet fighter produced after Korea went to a single weapon, away from a split 37mm/23mm payload. They had learnt the lesson.
> 
> The MiG-17 was the first Soviet fighter produced after Korea, and it had the combined armament for its entire service life, with the exception of radar-equipped aircraft which had the 37 mm cannon replaced by another 23 mm cannon to compensate for the additional weight of the radar and associated equipement.
> 
> I see a pattern there, Glider - play fair, or don't play at all.


The Mig 17 was not the first soviet fighter produced after Korea, the Mig 19 was and that switched to a common weapons system.

True the Mig 17 kept its weapons for its life but its my believe that that was also the case in the USAF.

I believe the following to be true. The USAF had the A and E which kept the 0.5 HMG, The F86D had rockets, The F86K had cannons but it was my understanding that this was for export only and not used in the USAF.
I certainly could be wrong and am happy to be corrected.

The USN had always been keen on the 4 x 20 and their aircraft were so armed but not the USAF.

Re Playing fair I have. Where I have made mistakes I have admited them and supported my statements. If that gets me half way to an ignore list, then I leave it to the people who are looking at this debate to make their own assumptions.


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## Kurfürst (Dec 20, 2008)

Glider said:


> I admit to having been doing some thinking and have some doubts about the statements being made.
> 
> For Example
> The 30mm Mk108 I do not see as being acurate up to 500m and then suddenly dropping off. Its a heavy shell with a low MV. Gravity will take over and the shell drop. The statement earlier in the thread that you can keep the pipper on the target up to 500m I frankly disbelieve.
> ...



You mistake accuracy for ballistic performance - they are not the same. The MK 108 was indeed very accurate with its short, stubby barrel and low muzzle velocity - accurate means the gun had very little dispersion. High muzzle velocity, long barelled _automatic_ guns, quite contrary to what instincts would tell you, are less accurate.

I have seen a LW accuracy table, and the ranking (from the most to the least accurate) was the follows:

MG FF
MK 108
MG 151
MK 103

The dispersion of the MK 103 was _twice_ that of the MG FF - the reason is barell flexing. Longer barrel, more powerful (ie. higher Mv) round - more flexing.


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## renrich (Dec 20, 2008)

Careful, Glider, or you will be relegated to the ignore list. As regards the ballistic coefficient of a projectile the relationship of length to diameter is important but also the form or the shape of the missile plays a big role. Of course gravity begins to act as soon as the missile leaves the muzzle but so does friction. The question I have had from the beginning is, based on illustrations I have seen, some of the cannon rounds appear to have a not very efficient shape or form as far as BC is concerned.


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## Glider (Dec 20, 2008)

Kurfürst said:


> You mistake accuracy for ballistic performance - they are not the same. The MK 108 was indeed very accurate with its short, stubby barrel and low muzzle velocity - accurate means the gun had very little dispersion. High muzzle velocity, long barelled _automatic_ guns, quite contrary to what instincts would tell you, are less accurate.
> 
> I have seen a LW accuracy table, and the ranking (from the most to the least accurate) was the follows:
> 
> ...



You are of course correct when you say that accuracy isn't the same as ballistic performance. However, although a longer barrel can mean more flexing that depends on the design of the gun. For instance the French 20mm was very accurate but also one of the longest cannon carried by any aircraft.
Also a short barrel with a powerfull cartridge can have an equally detremental effect on accuracy. It depends on how well matched the cartridge is matched to the gun.
Note - I am not saying this applies to the mk108 just making an observation about flexing


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## Glider (Dec 20, 2008)

renrich said:


> Careful, Glider, or you will be relegated to the ignore list. As regards the ballistic coefficient of a projectile the relationship of length to diameter is important but also the form or the shape of the missile plays a big role. Of course gravity begins to act as soon as the missile leaves the muzzle but so does friction. The question I have had from the beginning is, based on illustrations I have seen, some of the cannon rounds appear to have a not very efficient shape or form as far as BC is concerned.



Rennich
The Basllistic Coefficient is made up of two factors the Sectional Density and the Form Factor. 
The Sectional Density will favour the 30mm, its basically a calculation concerning the density of the shell and the frontal area of the projectile.

The Form Factor is basically the aerodynamics of the shell and is measured. I don't have the numbers but like you would be suprised if there is any significant difference between most shells of ww2.


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## renrich (Dec 20, 2008)

I have a source which has an actual sized illustration of four of the German 30 mm shells and three of the four appear to have a shape which would not lead to a high BC.


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## HoHun (Dec 20, 2008)

Hi Glider,

>Re Playing fair I have. 

If that was the best you could do, you're on ignore now.

Kind Regards,

Henning (HoHun)


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## kool kitty89 (Dec 20, 2008)

renrich said:


> I have a source which has an actual sized illustration of four of the German 30 mm shells and three of the four appear to have a shape which would not lead to a high BC.



http://www.ww2aircraft.net/forum/weapons-systems-tech/30mm-mine-shell-12821.html

Komet weapons: MK 108 cannon

The standard Minengeschoss shells were bunt nosed like their 20 mm counterparts (and fairly similar to their "normal" low capacity cousins -blunt from nose fuze)

The streamlined "Type N" shell (fitted with tracer) was much more streamlined, in fact it was probably the most streamlined cannon shell of the war. (in fact it apears to be better than the modern 20 mm HE shells used by the US millitary) The Shells of the British ADEN (and I assume the similar French DEFA) had rounds very much like the "Type N."

Even with the blunt shells the sectional density was quite high. (~40% higher that of the .50 Browning's round)



HoHun, I agree that the chemical and kinetic damage should be ranked seperately. (and HE vs Incendiary should probably be ranked seperately, and the varying characteristics of the HE or I compositions be taken into account as well, with incendiaries being particularly diverse: from phosphorus, to "flash powder" like pyrotechnic mixes, to thermite)

However I dostill think Momentum is a better measure of destructiveness than kinetic energy when looking at that alone. Of course that makes adding a cemical score trickier (though using the chemical energy is oversimpified in any case IMO) and still leaves the question on how to compare th two.

Ideally, you'd use a statistical analysis comparing the average number of hits from solid shot, and varying degrees of HE content (say ranging from 6 to 25% by mass) as well as incendiary mixtures in a similar manner. (possibly HE/I maxes as well)
Then compare such results through a variety of different caliber bullets/shells. 

Perhaps we should start a seperate thread on this.


I wonder if Soren has any thoughts on this, I seem to rember that he's pretty knoledgeable on this area. (particularly ballistics -which has admittedly spurred a few arguments when making comparisons of ballistics with aeordynamics of aircraft )


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## Glider (Dec 20, 2008)

Henning

Its a shame that you react this way when someone has a differing opinion and explains their case. I admitted when I made mistakes and its a shame that you don't feel able to do the same.

Nearly all my comments have been factual that you can check and I am open to correction. However you prefer to put me on an ignore list, that is your choice.

Until the next time


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## Glider (Dec 20, 2008)

kool kitty89 said:


> http://www.ww2aircraft.net/forum/weapons-systems-tech/30mm-mine-shell-12821.html
> 
> Komet weapons: MK 108 cannon
> 
> ...




The blunt shell would actually have basically little if anything, to do with the sectional density but it would have an impact on the Free Form which is about aerodynamics. 
Interestingly its the Tracer that has a large impact on the aerodynamics, as it causes an increase in pressure at the rear of the shell where there is an area of low pressure. As the shell passes through the air it creates a vacuum effect behind the shell, which in turn sucks in the air that the shell is passing through. This causes turbulence (drag) and the drag reduces efficiency. By increasing the pressure the tracer reduces the amount of turbulence and reduces the drag. As you would expect streamlining has a similar effect.


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## HoHun (Dec 20, 2008)

Hi Koolkitty,

>HoHun, I agree that the chemical and kinetic damage should be ranked seperately. (and HE vs Incendiary should probably be ranked seperately, and the varying characteristics of the HE or I compositions be taken into account as well, with incendiaries being particularly diverse: from phosphorus, to "flash powder" like pyrotechnic mixes, to thermite)

Well, if you come up with a method, and with the data required to feed it, I'll definitely have a thorough look at it  However, you're going to need a certain level of abstraction in order not to get swamped with detail, and that's what the energy-based method provides.

>However I dostill think Momentum is a better measure of destructiveness than kinetic energy when looking at that alone. 

Hm, why? The damage potential is limited by the kinetic energy, and as soon as you deviate from that, you already make an assumption regarding the damage mechanism, which depending on what the projectile will actually hit can be wrong as easily as right.

(The same problem applies to your suggestion of analysing the number of hits - unless you're talking about hits on actual aircraft, but we'd have to find something very specific there.)

Regards,

Henning (HoHun)


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## Soren (Dec 20, 2008)

Glider said:


> The blunt shell would actually have basically little if anything, to do with the sectional density but it would have an impact on the Free Form which is about aerodynamics.
> Interestingly its the Tracer that has a large impact on the aerodynamics, as it causes an increase in pressure at the rear of the shell where there is an area of low pressure. As the shell passes through the air it creates a vacuum effect behind the shell, which in turn sucks in the air that the shell is passing through. This causes turbulence (drag) and the drag reduces efficiency. By increasing the pressure the tracer reduces the amount of turbulence and reduces the drag. As you would expect streamlining has a similar effect.



Free Form ??? There's no such thing Glider.

Now if you were referring to the shape of the projectile then it's called the *Form Factor*, expressed as _i_ mathematically. And depending on which _i_ we're talking about, you also have to use different drag functions. (Either G1, 5, 6 or L)


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## Burmese Bandit (Dec 20, 2008)

A note on projectile design and specifically on tracer improving trajectory effectiveness: this is seen in modern artillery shells. Modern 155 shells have a 'boat tail' to smooth airflow going around the back, combined with what to a layman would look like a slow-burning rocket at the back - the technical term is 'base bleed'. This indeed does increase pressure at the back, but it does not directly reduce turbulence - instead it pushes the area where the turbulence begins further back from the base of the shell. This reduces drag.

The effect, however, does not show much dividends at short ranges. A shell with this base bleed effect does not show much advantage over conventional shells in terms of speed retained at short distances. It is in the LONG distances that the advantages begin to manifest themselves, which is why base bleed shells have a 10-15% range advantage over other types of shells at their maximum ranges...of course, at the expense of a reduction in payload.


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## kool kitty89 (Dec 21, 2008)

*Glider*, I know there are advantages with the tracer (post #101), as I posted here a while back, I also didn't mean to imply that there would be a difference between the SD of the blunt shell to the streamlined one. (just pointing out that there was a substancial SD advantage)

I also posted earlier on the cannon armmed F-86 (post #100), but it seems to have been overlooked. In addition to the cannon armmed F-86K interceptor, there were operational trials of the 4x M39 armament on F-86E's and F's in Korea as well (project Gonval).
Cannon-Armed F-86Fs

Most significantly there was the F-86H with 4x M39 armament as standard. North American F-86H Sabre


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## claidemore (Dec 21, 2008)

Soren said:


> Free Form ??? There's no such thing Glider.



Check post #114 Soren. Glider called it Form Factor there, I believe it was just a 'slip of the tounge' when he used the term Free Form.


As for the Mk108, it's trajectory was dismal, to say the last. 330 gram projectile starting out at 500 m/s, it will have dropped 40 meters at 1000 meters. Nobody in the Luftwaffe considered it a long range weapon, just a very effective short range one.


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## KrazyKraut (Dec 21, 2008)

I guess you asked every single one to be able to say that 


koolkitty said:


> On the HE machine gun rounds, there are a few reasons behind that statement (besides the "20 mm was determined to be the smallest caliber for a shell with worthwhile explosive capacity" statment -which is obviously debatable), The MG 131 HE round carried only 3.5% filler (1.2g) and the Italian-Vickers 12.7 mm even less at 2.2% (.73g) while the .50 BMG and .50 Vickers carry ~5% as pure incendiary rounds. ("de wild" derived)


That would imply that the particular incendiary machine gun rounds in question (esp. .50 BMG) simply carried more of the chemical agent than the explosive machine gun rounds of the opposite side and can thus be considered more effective, which makes sense.

However, I see no reason why incendiary rounds on heavy machine guns would be more effective than explosive rounds given all other variables being equal.


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## kool kitty89 (Dec 21, 2008)

I think it's just that the fuze took up so much space in such relatively small projectiles that the capacity of the rounds was very poor. 
Of course, you could go without the fuze, but then you remove the delay, use a more sensitive explosive (possibly risking premature detonation) so only surface damage is done. (or the round fails to detonate) And there are other possibilities, like a high capacity projectile made of drawn steel. (though this would also give further advantage as an unfuzed/incendiary round) But this is getting outside the scope of this thread. (possibly deserving of its own)

The Italian 12.7mm HE rounds are a good example as the ammo was a semi-rimmed export version of the .5" Vickers (12.7x81), though the projectile was of Italian design. So a good comparison between the Italian HE round and the British Incendiary round can be made.

As mentioned before, the Italian HE round contained 2.2% filler. (with a mass of 33g and 0.73g HE) 
The British Incendiary B Mark I.z (simplified "De Wilde") contained 5.3% filler (35.4 g and 1.94g HE)

The HE round can be seen below (far right): Untitled Document






And the Incendiary (right):


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## HoHun (Dec 21, 2008)

Hi Koolkitty,

>I also posted earlier on the cannon armmed F-86 (post #100), but it seems to have been overlooked. In addition to the cannon armmed F-86K interceptor, there were operational trials of the 4x M39 armament on F-86E's and F's in Korea as well (project Gonval).

"GUNVAL", actually - as pointed out in the article you linked, it was a direct response to pilot complaints about the 12.7 mm guns lacking firepower.

On "GUNVAL" by one of the participating pilots (LtCol. George L. Jones, 335 FIS, from "MiG Alley" by Larry Davis"):

"In the winter of 1952-53, several F-86s were fitted with 20mm cannon in an attempt to increase the effectiviness of the F-86 in combat. The six .50 calibre machine guns of the F-86 Sabre did not have the hitting power needed for a quick kill. The mission for the day was to find and engage the MiGs and combat test the effectivess of the new guns."

Everyone trying to tell you that the USAF was satisfied with the 12.7 mm gun in Korea is obviously attempting to mislead you, or has not done his homework properly.

Regards,

Henning (HoHun)


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## Glider (Dec 21, 2008)

kool kitty89 said:


> *Glider*, I know there are advantages with the tracer (post #101), as I posted here a while back, I also didn't mean to imply that there would be a difference between the SD of the blunt shell to the streamlined one. (just pointing out that there was a substancial SD advantage)
> 
> I also posted earlier on the cannon armmed F-86 (post #100), but it seems to have been overlooked. In addition to the cannon armmed F-86K interceptor, there were operational trials of the 4x M39 armament on F-86E's and F's in Korea as well (project Gonval).
> Cannon-Armed F-86Fs
> ...



I wasn't aware of the F86H being in such widespread use and I certainly didn't mean to overlook the posting.
Re the SD advantage it is substantial between the 0.50 and the 30mm but between the 20mm MkV and the 30mm its down to around 12%. This is a decent difference but nothing like the difference needed to make up for the difference in MV, where the 108 has around 2/3rds the MV of most 20mm guns. 
Almost inevitably the SD tends to go to the larger weapon.


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## HoHun (Dec 21, 2008)

Hi Claidemore,

>Nobody in the Luftwaffe considered it a long range weapon, just a very effective short range one.

Hm, what's your source for that?

A Luftwaffe study, published in Luftfahrt International 15 compares the low-velocity MK 108 battery installed in the Me 262 with a high-velocity battery consisting of 2 x MK 103 and 2 x MG 151 (15 mm) against Mosquito-sized jet bombers capable of a 750 km/h top speed, which the authors figured the Allies might field in the future.

The study concludes:

*"When a gyroscopic gunsight (corresponding to the future standard equipment!) is used, the battery of 4 MK 108 is still superior even at large angles-off-tail.* [emphasis original]

The MK 103 battery thus is not suited for conducting combat at longer ranges with better prospects. For gunnery against flying targets batteries of 4 MK 108 - even when combat against jet aircraft is considered - better than batteries of 2 MK 103 and 2 MG 151."

Here are the figures:


```
Combat range 800 m
Battery    Hits/s for angle-off-tail
Type       0 deg   15 deg   30 deg
2 MK 103:   0.24     0.22     0.17
2 MK 151:   0.39     0.36     0.27
4 MK 108:   0.49     0.45     0.29
```

As a large four-engined bomber flying at typical formation speeds was a much better target than a Mosquito-sized jet bomber, there should be little doubt that the MK 108 could successfully be used as an anti-bomber weapon at 800 m.

Figures for angle-off-tail 0, showing that the basic 1/r^2 range dependency of hit chances was not seriously affected by the MK 108's low muzzle velocity:


```
Battery    Fixed sight     Gyro sight 
Type       400 m   800 m   400 m   800 m
2 MK 103:   0.61    0.17    0.79    0.24
2 MK 151:   1.00    0.28    1.29    0.39
4 MK 108:   1.95    0.41    2.46    0.49
```

>As for the Mk108, it's trajectory was dismal, to say the last. 330 gram projectile starting out at 500 m/s, it will have dropped 40 meters at 1000 meters. 

As you can see, it was still an effective weapon at 800 m, but I think your comment highlights one problem of our discussion: We have no clear definition what "long range" actually means.

Since Blesse suggests to get within 1200 ft when attacking MiGs, the RAF report shows that 86 % of all their kills were achieved at 400 yards and less, and the typical convergence ranges of WW2 fighters were in the 200 - 300 m range, I'd say that it makes sense to consider everything above 400 m "long range". I guess much of the disagreement in this thread is in fact due to unrealistic ideas on the feasibility of what I'd call extreme-range fire (beyond 800 m).

Regards,

Henning (HoHun)


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## HoHun (Dec 21, 2008)

Hi Koolkitty,

>I think it's just that the fuze took up so much space in such relatively small projectiles that the capacity of the rounds was very poor.

Interesting consideration, thanks for pointing it out! 

The HE round can be seen below (far right): Untitled Document

Hm, someone should tell Tony that the word of his site would be better spread if he actually entered a title tag for his pages 

Regards,

Henning (HoHun)


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## Juha (Dec 21, 2008)

Hello HoHun
Interesting info but if the results are per battery, then from the first table 2* MK 103 plus 2*MG 151 got in 30 deg scenario 0,17+0,27=0,44 hits per sec and 4*MK 108 got 0,29. So how was 4*MK 108 battery more effective in hitting, maybe by delivering more HE on target even with fewer hits? And how was the figures achieved, by calculations, I guess.

We know from real world that PR Mossies were difficult targets to Me 262s, they didn't were content with flying straight and level but tried by violently manoeuvring to throw off Me 262 pilot's aim.

Juha


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## renrich (Dec 21, 2008)

I don't believe that anyone on this thread is claiming the US was satisfied with the armament of the F86. That misconception may be caused by a failure to thoroughly read posts or unfamiliarity with the English language. The facts are that the F86 was very successful against the Mig 15. Switching to 20 mm cannon was not however an unmixed blessing from a reliability point of view. One of my sources who operated the F8U mentioned that the care and feeding of it's 4-20mms was extremely complicated and not always successful. My source on the various German 30 mm shells has the MK 108(mine/tracer) with a MV of 1640 fps, and calls it self destructive. I assume that means it explodes upon contact. It is very blunt nosed, not spitzer shaped which would give it a poor BC. The Mk 108(incendiary) has a similar MV and is also self destructive and has the blunt nose. The MK 103(tungsten cabide core) has a MV of 3150 fps, is not self destructive but is meant for use against tanks. The projectile is spitzer shaped which would enhance BC. The Mk 103(incendiary/tracer) has a MV of 2950 fps, is not self destructive and has the blunt nose. It appears that all the rounds meant for air to air combat would have poor BCs and the two explosive rounds do not have a particularly high MV. In fact their MV is inferior to the MV of the Japanese Type 99 model 2 MK4 20mm cannon used in the A6M which had a MV of 1968 fps.


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## KrazyKraut (Dec 21, 2008)

Certainly the Mosquito was a difficult target as it was very maneouverable and the Me 262 not so. I don't see that changing with a different armament though. Especially the MK 103 I would imagine as being far worse because of the much lower ROF.


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## Burmese Bandit (Dec 21, 2008)

"...My source on the various German 30 mm shells has the MK 108(mine/tracer) with a MV of 1640 fps, and calls it self destructive. I assume that means it explodes upon contact..."

Renrich, AFAIK 'self destruct' means that the shells explode if they don't hit anything within a certain period of time. AFAIK the Germans added this feature to their shells so that shells which did not hit any target and falling out of the sky over germany would not explode in their own german towns and villages.


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## Glider (Dec 21, 2008)

Hennings numbers are intresting but against a target trying to evade the fire the hit ratio would be much lower due to the time of flight.

However there is one point that springs to mind. The comparison was one aircraft with 4 x 30mm mk 108, the other 2 x 30mm mk103 and 2 x 15mm 151.

The sight on the aircraft with a standard battery would be configured against the 30mm Mk 108,
The sight on the other aircraft would have to be set against a compromise to allow for the different ballistics of each weapon. This is of course one of the problems of having mixed weapons, neither weapon will do as well as if they were on their own.


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## KrazyKraut (Dec 21, 2008)

renrich said:


> I don't believe that anyone on this thread is claiming the US was satisfied with the armament of the F86. That misconception may be caused by a failure to thoroughly read posts or unfamiliarity with the English language.


The F86's armament was lacking, the MiG's armament was overall better. That this fact is not clearly admitted but dodged by leading the argument astray and ad absurdum is what causes confusion. Not a lack of English or reading skills.


> The facts are that the F-86 was very successful against the Mig 15. Switching to 20 mm cannon was not however an unmixed blessing from a reliability point of view. One of my sources who operated the F8U mentioned that the care and feeding of it's 4-20mms was extremely complicated and not always successful.


See, this is what I mean. 



> My source on the various German 30 mm shells has the MK 108(mine/tracer) with a MV of 1640 fps, and calls it self destructive. I assume that means it explodes upon contact. It is very blunt nosed, not spitzer shaped which would give it a poor BC.


Define poor. The MK 108's shells all had a very high sectional density, which alone should give them an acceptable BC. The 108's HE shells vary in terms of form factor, with the Ausf. C looking more streamlined than, for example, a 20x110 (HS.404) HE round. But that is debatable.



> The MK 103(tungsten cabide core) has a MV of 3150 fps, is not self destructive but is meant for use against tanks. The projectile is spitzer shaped which would enhance BC.


The point is rather to improve penetration.


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## renrich (Dec 21, 2008)

BB, Thanks for clarifying. I have wondered about the effect that the shells and bullets that missed must have had on the ground below.


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## Soren (Dec 21, 2008)

claidemore said:


> Check post #114 Soren. Glider called it Form Factor there, I believe it was just a 'slip of the tounge' when he used the term Free Form.



Maybe, but it still strikes me as a very odd misspelling.



> As for the Mk108, it's trajectory was dismal, to say the last. 330 gram projectile starting out at 500 m/s, it will have dropped 40 meters at 1000 meters. Nobody in the Luftwaffe considered it a long range weapon, just a very effective short range one.



Sorry but that's just pure rubbish Claidemore. The Mk108 was considered a very effective weapon for long range shooting by the LW, one of the most accurate.


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## Soren (Dec 21, 2008)

Burmese Bandit said:


> A note on projectile design and specifically on tracer improving trajectory effectiveness: this is seen in modern artillery shells. Modern 155 shells have a 'boat tail' to smooth airflow going around the back, combined with what to a layman would look like a slow-burning rocket at the back - the technical term is 'base bleed'. This indeed does increase pressure at the back, but it does not directly reduce turbulence - instead it pushes the area where the turbulence begins further back from the base of the shell. This reduces drag.
> 
> The effect, however, does not show much dividends at short ranges. A shell with this base bleed effect does not show much advantage over conventional shells in terms of speed retained at short distances. It is in the LONG distances that the advantages begin to manifest themselves, which is why base bleed shells have a 10-15% range advantage over other types of shells at their maximum ranges...of course, at the expense of a reduction in payload.



Very true BB. That is why the Germans opted for heavy boat tailed projectiles as their std. rifle projectiles. The German sS projectile for example, which by late 44 was restricted for Snipers mostly, is even by todays standards an extremely slick stable projectile, easily outperforming the 7.62mm M118 M72 match round used as the std. Sniper rounds today. The BC of the 198gr sS projectile ranges from .557 to .584, compared to the .505 to .530 of the 173gr M72 and .480 to .507 of the 168gr M118. 

As for tracers having reduced drag, well not regular tracer bullets, infact the loss in mass because of the phosphor burning away causes the SD to drop and with it the BC. Therefore tracer rounds usually have a shorter maximum range than the regular rounds.


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## HoHun (Dec 21, 2008)

Hi Juha,

>Interesting info but if the results are per battery, then from the first table 2* MK 103 plus 2*MG 151 got in 30 deg scenario 0,17+0,27=0,44 hits per sec and 4*MK 108 got 0,29. So how was 4*MK 108 battery more effective in hitting, maybe by delivering more HE on target even with fewer hits? 

Yes, the 30 mm hits were of course much more effective than the 15 mm hits, so the MK 108 came out on top.

>And how was the figures achieved, by calculations, I guess.

The fixed sight errors were based on data from cine-gun films, the gyro gunsight errors were based on the experiences of the Erprobungsstelle, the average tracking error was based on frontline film evaluation ("by Dr. Th. W. Schmidt" - perhaps this is a lead for further research), and the weapon dispersion (considered the least influential parameter) was based on the measured pattern of the Me 262 battery and on parameters based on the experience of the Erprobungsstelle Tarnewitz for the MK 103/MG 151 battery. Of course, you can't consolidate all of that data without some calculation, but the data is as realistic as it's going to get - and the Luftwaffe experts were genuinely interested in finding the best available armament option, not in bashing someone on the internet.

>We know from real world that PR Mossies were difficult targets to Me 262s, they didn't were content with flying straight and level but tried by violently manoeuvring to throw off Me 262 pilot's aim.

Absolutely ... an evading Mosquito would require closing to short range for realistic chances for a kill, and the Mosquito would still have the manoeuvrability advantage typical for propeller-driven aircraft there. However, the report I quoted considered fast jet bombers, and that would change the game a bit.

Regards,

Henning (HoHun)


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## renrich (Dec 21, 2008)

Let us examine some ballistics numbers from the Nosler handloader manual. Compare two bullets-.308 cal. 180 grain spitzer with a sec. den. of .271 and a bal. coef. of .456 and the 180 gr protected point( which has a similar shape to the 30 mm projectiles except for the tungsten core one, in other words is blunt nosed) The PP bullet has a sec. den. of.271, and a bal. coef. of .355. Performance wise if both bullets start out at 2800 fps, the spitzer has a time of flight to a target at 500 yards of .6568 seconds and a bullet drop from the muzzle of 72.8 inches. The PP bullet respectively has a time of flight of .7002 seconds and drop from muzzle of 79.6 inches. Starting with a MV of 1800fps, the spitzer has a TOF of 1.0422 seconds and a bullet drop of 181.7 inches, whereas the PP has respectively 1.103 seconds and 199.2 inches. Obviously I don't have the ballistics for the 30 mm shells but one can see that the form factor has a big influence on the trajectory and time of flight.


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## Glider (Dec 21, 2008)

Soren said:


> Maybe, but it still strikes me as a very odd misspelling.


It was a mistype Soren. I have been working with a company called Free Form, these things happen 


> Sorry but that's just pure rubbish Claidemore. The Mk108 was considered a very effective weapon for long range shooting by the LW, one of the most accurate.



I take it that you can support this statement Soren.

If the 30mm Mk108 was considered such a good long ranged weapon, why did they try fitting a 50mm to it?
Also why did the Germans go to such trouble to fit the Mk103 into Fw190's? 
Finally why did the Germans even think of putting higher velocity Mk 103 and Mk 151 15mm into the 262?


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## Soren (Dec 21, 2008)

The answer is simple Glider: A shorter flighttime. The Mk103 would've made deflection shooting in dogfights easier. But that's not what we were discussing, we were discussing ballistics accuracy, and the Mk108 was one of the more accurate guns put on LW a/c.

Now to top it off you simply have no proof that the accuracy or ballistics of the 30mm Mk108 was bad. I on the other hand have the LW pilots opinion which makes it quite clear that the Mk108 was one of the most accurate guns.


HoHun has also presented a study from Luftfahrt 15 which shows the superior accuracy of the Mk108, even in deflection shooting. So what is your source for saying the opposite besides opinion?


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## Glider (Dec 21, 2008)

Soren said:


> The answer is simple Glider: A shorter flighttime. The Mk103 would've made deflection shooting in dogfights easier. But that's not what we were discussing, we were discussing ballistics accuracy, and the Mk108 was one of the more accurate guns put on LW a/c.


Trying a Mk103 in a dogfight is at a disadvantage due to the low rate of fire and the huge amount of extra weight which would also ruin performance. 
Also the concept of trying a 50mm as a dogfighting weapon is unthinkable. Th only reason you would try a 50mm is if you wanted to fire at long range. Which if the 108 was so good at long range, would not be required. 



> Now to top it off you simply have no proof that the accuracy or ballistics of the 30mm Mk108 was bad. I on the other hand have the LW pilots opinion which makes it quite clear that the Mk108 was one of the most accurate guns.


Look at Hennings chart on posting 22. That shows you the poor balistics at any range. 

Read the explanation in posting 28 for the reason for the dip.



> HoHun has also presented a study from Luftfahrt 15 which shows the superior accuracy of the Mk108, even in deflection shooting. So what is your source for saying the opposite besides opinion?


Accuracy is one things, accuracy at range is another. The Mk 108 may well be accurate but I don't believe that it has range.

Now if I could ask you to supply the details of those pilots who believed the mk108 to be accurate at long range, I would appreciate it.


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## Juha (Dec 21, 2008)

Hello HoHun

Thanks for the background info on the LW study. Much appreciated.

Quote:” the Luftwaffe experts were genuinely interested in finding the best available armament option…”

Of course that was/is the function of operational studies. But sometimes the studies of different nations got slightly different results. If you look Tony’s Flying Guns WWII p. 41-42 You will notice that British conclusion after tests against British a/c was that “although German M-Geschoss contained more explosive, the powerful Hispano [with HEI] stood more chance of doing serious damage – such as the breaking of spar flanges – or of reaching the fuel tanks.” 

Tony’s conclusion is that whether a Hispano HEI or 20mm M-Geschoss would do more damage depended on the a/c being attacked and exactly where the shell detonated.

Soren
if you study the tables in HoHun’s message # 129, you will notice that in fact MK 103 was significantly more accurate in deflection shooting at 800m, if we definite accuracy as how high % of fired shells hit the target. At 30 deg deflection one MK 103 even got more hits per sec than one MK 108, even if 103 had much lower ROF. And even at 0 deg deflection the number of hits per sec was almost the same, 0,12 vs 0,1225 per sec and so MK 103, because it got its results with fewer shells, was more accurate. On the other hand MK 108 was clearly more efficient in that IIRC two MK 108 with ammo weighted more or less as much as one MK 103 with ammo, so one got clearly more hits per given weapon installation weight.


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## HoHun (Dec 21, 2008)

Hi Juha,

>If you look Tony’s Flying Guns WWII p. 41-42 You will notice that British conclusion after tests against British a/c was that “although German M-Geschoss contained more explosive, the powerful Hispano [with HEI] stood more chance of doing serious damage – such as the breaking of spar flanges – or of reaching the fuel tanks.” 

>Tony’s conclusion is that whether a Hispano HEI or 20mm M-Geschoss would do more damage depended on the a/c being attacked and exactly where the shell detonated.

Hm, though I'm sure the British report on German weaponry was prepared with professional care too, the situation is a bit different than with German experts evaluating German weapons. The British did not have the full background on the Luftwaffe mine shell concept, which had been developed under consideration of just the points listed by Tony. Within its scope, the British report gave a correct answer, but the Germans had answered the additional question of how likely each type of hit was, and concluded that the mine shell was superior to other shells. This was the result of additional research unknown to the British experts, so there is really no fault in their analysis, it's just that it is not exhaustive to the subject.

Regards,

Henning (HoHun)


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## Juha (Dec 21, 2008)

Hello HoHun

Quote:"This was the result of additional research unknown to the British experts, so there is really no fault in their analysis, it's just that it is not exhaustive to the subject."

Well, true, but on the other hand Germans didn't have access of the results of the British practical shooting tests either. British results and the reasons of Tony's conclusion seemed reasonable to me in light of what I learned and saw while serving as combat engineer. Over ½ of page 42 is on these differences between the effects of M-Geschoss and 20mm Hispano HEI. A bit same difference was between KM's 127mm and RN's 120mm shells and their fuzing. Seems that Germans had bit different approach to the question what was the most effective way to achieve the most destructive damage to the target than Brits.

Juha


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## Soren (Dec 21, 2008)

Glider, you should read some of the LW after action reports. 

As for bullet drop, the 30mm shells from the Mk108 dropped about 30m at 1,000m. 





Now besides pure assumption, what is it that makes you claim that the Mk108 was inaccurate at range ? Do you have any specific proof Glider ?


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## Glider (Dec 21, 2008)

Soren
I never questioned its accuracy, but I did question its range and it depends if you think a 31 meter drop is good but its an interesting chart. Where do you get them as I would be interested in getting some copies.
Re the after battle reports I am happy to read them if you can point me in the right direction.


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## HoHun (Dec 21, 2008)

Hi Juha,

>Well, true, but on the other hand Germans didn't have access of the results of the British practical shooting tests either. 

Well, the German experts didn't compare British rounds to Luftwaffe rounds, but rather conventional high-explosive rounds (similar but not identical to the Hispano's) to mine shells of the same calibre. They found these mine shells to be superior for air-to-air fire for all guns of 20 - 30 mm calibre, both low-velocity guns like the MG FF and high-velocity guns like the MK 103. I'm sure that had a mine shell existed for the Hispano cannon, it would have been found superior to the high-explosive shell too. What's more, the Germans - unlike the British - actually had extensive combat experience with all these types of guns, so that they could validate their findings. Even the Schießfiebel gunnery textbook took care to point out that the standard beltings (with high mine shell count) were 'well proven' ("bewährt").

The British based their conclusion on a rather slim data basis: "For comparison purposes a few rounds of 20 mm Hispano HEI was fired at the same target as above."

(One aspect not to forget is that the MG 151/20 had a 20% rate of fire advantage over the Hispano II, so that even with shells of equal destructiveness, it would still retain an advantage.)

>Over ½ of page 42 is on these differences between the effects of M-Geschoss and 20mm Hispano HEI. 

Hm, except for the paragraph we already quoted, the left-hand column is mostly on 30 mm mine shells and their effects on Spitfire and Blenheim fuselages. 

(Interesting in this context: I had been well aware of the popular "destroyed Spitfire" and "destroyed Blenheim" picture, but I had had no idea that the experiement had been repeated 10 times for the Spitfire and 11 times for the Blenheim. Score: 3 Spitfires immediately lethal, 7 Spitfires probably lethal. 3 Blenheims immediately lethal, 7 Blenheims probably lethal, 1 Blenheim doubtful.)

The right hand column has a description of Hispano effects on the target, followed by Tony's conclusion which you already quoted. The mine shell is only mentioned because produces smaller and lighter fragments than the Hispano shells, but as the "very-high-velocity, very small fragments" of the MK 108 mine shell had proven quite devestating in the US test against a B-24 fuselage, cutting control cables and fuselage longerons, I'd not consider that a disadvantage.

I don't think we can really conclude much more than we already did from that page - but maybe Tony is lurking and could provide more details for us? 

Regards,

Henning (HoHun)


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## kool kitty89 (Dec 22, 2008)

renrich said:


> Switching to 20 mm cannon was not however an unmixed blessing from a reliability point of view. One of my sources who operated the F8U mentioned that the care and feeding of it's 4-20mms was extremely complicated and not always successful.
> 
> The Crusader used the Colt Mk.12 cannon, a gun based on the Hispano, but with a rate of fire of ~1,000 rpm, it used ammunition similar to the USAF's used on the M39 and later M61 (derived from the WWII .60 cal ATR) but with a case lenthened from 102 to 110 mm and fired a heavier projectile at a slightly lower velocity. The reliability problems seem to have been resulted to the feed system as you mentioned, being particularly sensitive to high-G maneuvers (also a problem on the Pre-D P-51's .50's). I'm not sure how the reliability of the M3 (used just afer WWII and by the USN in Korea) or M24 Hispano would compare for reliability, but I expect they'd be better.
> 
> My source on the various German 30 mm shells has the MK 108(mine/tracer) with a MV of 1640 fps, and calls it self destructive. I assume that means it explodes upon contact. It is very blunt nosed, not spitzer shaped which would give it a poor BC. The Mk 108(incendiary) has a similar MV and is also self destructive and has the blunt nose. The MK 103(tungsten cabide core) has a MV of 3150 fps, is not self destructive but is meant for use against tanks. The projectile is spitzer shaped which would enhance BC. The Mk 103(incendiary/tracer) has a MV of 2950 fps, is not self destructive and has the blunt nose. It appears that all the rounds meant for air to air combat would have poor BCs and the two explosive rounds do not have a particularly high MV. In fact their MV is inferior to the MV of the Japanese Type 99 model 2 MK4 20mm cannon used in the A6M which had a MV of 1968 fps.



The velocity figure for the Type 99-2 apears to be a figure for the Type 99-1 (600 m/s or 1968 ft/s) while that of the Type 99-2 should be 750 m/s or 2460 ft/s. (note the Type 99-1 and -2 are licensed derivatives of the Oerlikon FFF and FFL respectively)


The "self destruct" was, as Burmese Bandit mentioned, is a HE shell that detonates automatically after a certain period to avoid shells falling to the ground over friendly territory.

There was also a more streamlined "Type N" minengeschoss (with tracer) as I mentioned earlier, also I mentioned a thread discussing this and a page with info on the MK 108's ammo:


kool kitty89 said:


> http://www.ww2aircraft.net/forum/weapons-systems-tech/30mm-mine-shell-12821.html
> 
> Komet weapons: MK 108 cannon


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## Juha (Dec 22, 2008)

Hello HoHun

Quote:” The British based their conclusion on a rather slim data basis: "For comparison purposes a few rounds of 20 mm Hispano HEI was fired at the same target as above."”

Now British had made numerous tests with different Hispano ammos, so they had pretty good info on effects of those, incl HEI, beforehand.

Quote:” (One aspect not to forget is that the MG 151/20 had a 20% rate of fire advantage over the Hispano II, so that even with shells of equal destructiveness, it would still retain an advantage.)”

Now Hisso V had the same ROF or a bit better than MG 151/20. But of course Mk V was a bit later cannon.

Also important in the text were the effects on Hisso’s 20mm HEI on armour and whatever was behind it the effects of very near detonation on self-sealing fuel tank. As we know the self sealing worked better against numerous tiny holes than fewer bigger holes.

Juha


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## HoHun (Dec 22, 2008)

Hi Juha,

>Now British had made numerous tests with different Hispano ammos, so they had pretty good info on effects of those, incl HEI, beforehand.

Hm, you have sort of a point there, but on the other hand, that they fired the extra Hispano rounds in the course of the mine shell comparison mentioned by Tony shows that they didn't actually have their data in a form that would have allowed a systematical analysis without extra firing trials, so I'd still consider they conclusion a bit shaky.

>Now Hisso V had the same ROF or a bit better than MG 151/20. But of course Mk V was a bit later cannon.

You're right, and it's just my assumption that they most likely tried it against a Hispano II projectile. The Hispano V had a better rate of fire, but the projectiles lost a bit of power due to the lower muzzle velocity, and as the late war MG 151/20 received the improved MX mine shell, it also increased its firepower. 

The muzzle firepower data:

MG 151/20 (MX): 1,40 MW
MG 151/20: 1,27 MW
Hispano V: 1,23 MW
Hispano II: 1,06 MW

So the step up from the Hispano II to the Hispano V was about the same as that of the MG 151/20 with 3:5 mine shells to that with 3:5 MX shells.

>Also important in the text were the effects on Hisso’s 20mm HEI on armour and whatever was behind it the effects of very near detonation on self-sealing fuel tank. As we know the self sealing worked better against numerous tiny holes than fewer bigger holes.

Roger, but if we're talking about an large number of very small, very-high-speed fragments that were capable of cutting fuselage longerons, I'm not sure that the result wouldn't be a big hole too.

However, the mine shell is primarily designed to attack the aircraft structure which makes up the greatest share of the target area, and damage against critical components, which make up a smaller share of the target area, is secondary. Armour piercing capability for example is zero, and this is accepted as there is only little armour on an aircraft, but large unarmoured areas that can be damaged very effectively by the maximized (for the respective calibre) blast effect of the mine shells.

An article in Luftfahrt International 7 describes blast damage experiments against aircraft components conducted in Tarnewitz, and the findings of those experiments describe the core idea of the mine shell concept: 

"The mine shell ammunition for 2 cm and 3 cm projectiles increased the share of the completely destroyed surface in relation to the total surface to 60% for fighters and 30% for bombers."

So even if you have a projectile that does more damage against critical components than the mine shell, as long as the critical components make up less than 60% of the target area for fighters, and less than 30% of the target area for bombers, the mine shell will be more destructive overall.

The Luftwaffe squadrons could verify this easily by merely changing the belting order in their fighters as the traditional projectiles were still available to them and in common use (for example for use against ground targets), and as the hints in the Schießfiebel indicate, were not above a little experimenting to get the best effect from their guns. That the mine shell stayed the Luftwaffe's primary round for air-to-air combat simply shows that it was the best round for air-to-air combat - it had been selected in direct competition against traditional shells because of its merits in actual combat.

Regards,

Henning (HoHun)


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## Kurfürst (Dec 22, 2008)

Juha said:


> Also important in the text were the effects on Hisso’s 20mm HEI on armour and whatever was behind it the effects of very near detonation on self-sealing fuel tank. As we know the self sealing worked better against numerous tiny holes than fewer bigger holes.
> 
> Juha



I think we miss the fact in this discussion that the MG 151 fired both high-capacity, thin walled M-Geschoss and the ordinary thick walled HE/HEI akin the Hispano's HEI round.


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## claidemore (Dec 22, 2008)

I just think it is odd that even though the Luftwaffe considered that it took 25 to 35 hits from a 20mm cannon to down a 4 engine bomber, (which with the 'accurate' centrally mounted Mg151/20 is only a 2 - 3 second burst), they still felt it nescessary to add two more cannon with 'inaccurate' gondola wing mounts on the Me109. 

This would indicate that combat experience showed that the accurate centrally mounted gun was not good enough, and that adding a couple wing guns with their corresponding convergence variance, increased hit probability and combat effectiveness.


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## Juha (Dec 22, 2008)

Hello HoHun
all I would say that MG 151/20 and Hisso Mk V were almost as effective, which was better I cannot say and anyway in real combat the difference was probably meaningless. Much depended on circumstances, for average pilot MG 151/20 with M-Geschoss was probably better and also if one was attacking USAAF heavy bomber or B-26 Marauder; in case of a good shot attacking Blenheim or Ju 88, I maybe dare to say that Hisso would have been usually better because its ability to pierce armour, if one was aiming into cockpit and because of bigger fragments of its shell were more likely to make fatal damage to engine, if one was aiming engines. A good shot against fighter, now probably most fighters shot down were those whose pilots didn’t see the attacker in time, so as above but if seen in time maybe M-Geschoss was better because against violently manoeuvring fighter the attacker would have been happy to got in some hits somewhere. Against Wellington Hisso would have been better and probably also against Il-2. These thoughs are only opinions, nothing more.

Hello Kurfürst
You are rignt, but because Hisso fired heavier shell with higher MV, its HEI probably was more effective.

Juha


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## HoHun (Dec 22, 2008)

Hi Claidemore,

>I just think it is odd that even though the Luftwaffe considered that it took 25 to 35 hits from a 20mm cannon to down a 4 engine bomber, (which with the 'accurate' centrally mounted Mg151/20 is only a 2 - 3 second burst), they still felt it nescessary to add two more cannon with 'inaccurate' gondola wing mounts on the Me109.

You're assuming 100 % hit rate there  I'm sure the Luftwaffe wouldn't have worried about extra guns if their pilots could shoot that accurate, but the hit rate figure they were realistically expecting was less than 10 % (9 % at a combat range of 500 m in one report, 5 % with no range specified in another.)

The report specifying the combat range of 500 m points out that for a 95% probability of a kill, the attacking fighter would have to fire 275 rounds. That would take 23 seconds ... not a good idea to hang around for so long in the sights of multiple tail gunners.

>This would indicate that combat experience showed that the accurate centrally mounted gun was not good enough, and that adding a couple wing guns with their corresponding convergence variance, increased hit probability and combat effectiveness.

For anti-bomber combat, certainly - I don't think anyone would disagree. I'd even say that the single 20 mm nose cannon was a bit on the weak side against fighters too, but before this opinion gets misunderstood, I'd like to point out that it was still a better setup than the P-51D's:

Me 109G-6: 1,8 MW
P-51D: 1,7 MW

(Not because of the neglegible 0.1 MW advantage, but because the cannon was centrally mounted and had no convergence issues.)

Regards,

Henning (HoHun)


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## HoHun (Dec 22, 2008)

Hi Juha,

>all I would say that MG 151/20 and Hisso Mk V were almost as effective, which was better I cannot say and anyway in real combat the difference was probably meaningless. 

Absolutely - and your conclusion does in fact agree closely with the total-energy-based evaluation:

2x MG 151/20 - 388 rpg, 32 s duration - 250 kg - 2,54 MW firepower - firepower per weight: 10,15 kW/kg
2x Hispano V - 337 rpg, 28 s duration - 250 kg - 2,47 MW firepower - firepower per weight: 9,88 kW/kg

(I had to add an extra digit of accuracy to show any firepower difference at all 

Just for grins, here a 12.7 mm battery of the same weight for comparison:

4x ,50 Browning M2 - 305 rpg, 23 s duration - 250 kg - 1,1 MW firepower - firepower per weight: 4,5 kW/kg

>in case of a good shot attacking Blenheim or Ju 88, I maybe dare to say that Hisso would have been usually better because its ability to pierce armour, if one was aiming into cockpit and because of bigger fragments of its shell were more likely to make fatal damage to engine, if one was aiming engines. 

It's always possible to design a scenario where the one gun is better than the other, and if you're able to aim at a specific part of the plane, that's an overkill situation anyhow. (I don't think that the armour of a Ju 88 was capable of stopping either 20 mm.) Aiming at a specific part of the plane is easier with a centreline-mounted gun is easier, by the way, so the synchronizable MG 151/20 has some advantage here, too.

>Against Wellington Hisso would have been better and probably also against Il-2. These thoughs are only opinions, nothing more.

I agree on the Wellington, it's quite clear that the special construction method was not as vulnerable against mine shells as stressed-skin aircraft. I also agree partially on the Il-2, as the Hispano ammunition would undoubtly be better at piercing the armour tub. 

On the other hand, the Il-2 wings were just as vulnerable to mine shells as most, and the wooden wings of the early variants were highly vulnerable because wood responds with rapidly spreading cracks to blast damage that unlike shears in sheet metal consume very little energy as they propagate.

But now we're getting very specific 

>You are rignt, but because Hisso fired heavier shell with higher MV, its HEI probably was more effective.

I agree, for a single Hispano II shell I've got 106 kJ according to Tony's data, while the MG 151/20 HET achieved just 50.3 kJ and the HEI 50.6 kJ.

The MG 151/20 really scores by higher rate of fire and the use of mine shells, which yield 142 kJ for the early version and 161 kJ for the MX version.

Regards,

Henning (HoHun)


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## Kurfürst (Dec 22, 2008)

Juha said:


> Hello Kurfürst
> You are rignt, but because Hisso fired heavier shell with higher MV, its HEI probably was more effective.
> 
> Juha



Why...?


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## claidemore (Dec 22, 2008)

Hi Henning, 



> You're assuming 100 % hit rate there I'm sure the Luftwaffe wouldn't have worried about extra guns if their pilots could shoot that accurate, but the hit rate figure they were realistically expecting was less than 10 % (9 % at a combat range of 500 m in one report, 5 % with no range specified in another.)



This is my argument in a nutshell. With only 10-5% accuracy, convergence issues really aren't an issue at all, in fact they will probably increase hit probability with the 'box' harmonization. The less accurate system (sic), will be more effective in combat. 

I think the graphs in post #65 can be used to show that quite clearly. Move the target plane around on the graph erratically, and smaller 'circle' of the nose mounted guns will be off target more often than the larger, and often twin 'circles' of the wing mounted guns. Admittedly with less damage than a concentrated centrally mounted multi gun installation, but a miss is a miss and any hit is better than a miss. 

Basically a large 'box' harmonization of wing mounted guns would be capitalizing on the 90-95% expectation of missing the target, and turning that into a hit probability.

I am presently working in sales, and there is an 80/20 rule that states that 20% of clients buy, so most sales people concentrate on the 20%. But it's the sales people that work on the 80% that excell. 

With aerial combat, that means either more guns spread out over a wider area, or more accurate shooting (computerized sights).


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## HoHun (Dec 22, 2008)

Hi Claidemore,

>I think the graphs in post #65 can be used to show that quite clearly. Move the target plane around on the graph erratically, and smaller 'circle' of the nose mounted guns will be off target more often than the larger, and often twin 'circles' of the wing mounted guns. 

>Admittedly with less damage than a concentrated centrally mounted multi gun installation, but a miss is a miss and any hit is better than a miss. 

Convergency/divergence or a larger pattern will not increase kill probabilities even when large errors are preset.

The reason is that the hit chances fall off with the distance to the target centre, and the average distance to the target centre is always greater with the guns off centre than with the centreline gun for a centre-weighted distribution (and you clearly have a Gaussian distribution here ... "bell curve", you're probably familiar with this one).

Regards,

Henning (HoHun)


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## slaterat (Dec 22, 2008)

I tend to agree with Claidemore , once you get to the heavier armed fighters a box convergence has real benefits. I'd pick the tempest with 4 wing mounted hispanos and a good ammo load. Theres no syncronization to slow down rate of fire and varying tragedtories of different weapons to worry about. The logistics are easier too.

Slaterat


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## HoHun (Dec 22, 2008)

Hi Slaterat,

>I tend to agree with Claidemore , once you get to the heavier armed fighters a box convergence has real benefits. 

It's the heavier armament, not the convergence/divergence that has the benefits. In direct comparison of equal batteries, centreline armament always is superior.

As noted above, no fighter has ever been designed to mount the guns farther out in the wings than absolutely necessary. The 8-gun Hurricane's gun layout has always been considered superior to the 8-gun Spitfire's, for example.

Regards,

Henning (HoHun)


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## drgondog (Dec 22, 2008)

HoHun said:


> I'd even say that the single 20 mm nose cannon was a bit on the weak side against fighters too, but before this opinion gets misunderstood, I'd like to point out that it was still a better setup than the P-51D's:
> 
> Me 109G-6: 1,8 MW
> P-51D: 1,7 MW
> ...



So, against fighters you would take one centrally mounted 20mm in lieu of 6 x50 cal in wings?

One shell vs six - *all* capable of breaking a spar or killing a pilot or destroying an engine. Assuming each had at least one gun properly boresighted to hit what you are aiming at a 200 yards, the six gun Mustang has 5 more projectiles 'in the area' - some hitting the target -some near misses.

Interesting.


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## Soren (Dec 22, 2008)

I think a single .50 cal round would have a very hard time ruining an engine from stern shots, and it wouldn't penetrate the pilots armour AFAIK. The .50 cal round wasn't at all the most destructive of rounds, and it often took alot to down a fighter.

But that having been said I'm not sure if I'd want a single central mounted 20mm cannon over six wing mounted .50 cal HMG's, the sheer amount of lead the six HMG's are spewing out should maen more hits pr. second, regardless of convergence. 

Now give me two central mounted 20mm cannons, that I'd take over six .50 cal HMG's any day, the 20mm cannon simply does a whole lot more damage pr. round.


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## KrazyKraut (Dec 22, 2008)

drgondog said:


> So, against fighters you would take one centrally mounted 20mm in lieu of 6 x50 cal in wings?
> 
> One shell vs six - *all* capable of breaking a spar or killing a pilot or destroying an engine. Assuming each had at least one gun properly boresighted to hit what you are aiming at a 200 yards, the six gun Mustang has 5 more projectiles 'in the area' - some hitting the target -some near misses.
> 
> Interesting.


You are forgetting about the two centrally mounted 13mm MGs apparently.

1x20mm plus 2x13mm centrally mounted vs. 6x12.7mm is not that different. Given the nature of '44 air combat I'd take the platform with more guns. However i'd take 2x20mm and 2x13mm centrally mounted over both any day.


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## Juha (Dec 22, 2008)

Hello Kurfürst
I assume that the Hisso’s shell, being heavier and faster, was better against armour and so more dangerous to things behind the armour. Also heavier shells produces higher weight of fragments or it has more HE inside, usually both. And heavier and faster shell penetrates deeper into target before exploding if fusing is same. 
That doesn’t necessary means that Hisso was better gun, only that the philosophies behind the two guns were slightly different, 151 counted more on blast and numerous small fragments and Hisso more on kinetic energy and fewer but heavier fragments. 

Juha


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## Kurfürst (Dec 22, 2008)

Juha said:


> Hello Kurfürst
> I assume that the Hisso’s shell, being heavier and faster, was better against armour and so more dangerous to things behind the armour. Also heavier shells produces higher weight of fragments or it has more HE inside, usually both. And heavier and faster shell penetrates deeper into target before exploding if fusing is same.



That's the part I don't get - its not a AP or solid shell. Its a shell that blows up upon/very shortly after impact. As a result

1, Its capability is marginal against armor because of its construction, and because by the time it would reach armor the fuse blows it into tiny bits of fragments. 

2, Heavier and/or faster does not particularly effect how 'deep' it penetrates into the fuselage (as this a matter of fuse timing, achieving a desired distance) and, with the fuselage being a hollow, very thin layer of aluminium skin and not some body or piece of dense, solid structure, its isn't particularly hard to punch true - I guess even a .22 LR round would be more than capable of that, _not to speak of the capabilities a 20mm round_. 

And course, the amount of damage done is proportional to the amount of energy required to yield that damage to the structure. In the case of the same damage, the energy is the same and very likely very much smaller than the total energy the shell possesses, given light aircraft structure. 

For example, if lets say, a spar flange requires 2000 Joules to have punched a 20mm diameter hole in it, in practical matter it doesn't really matter if you have 20 000 or 25 000 Joule KE round for the task, since the only difference will be that, to simplify matters, that the less powerful round will continue its path once it exited the aircraft with 18 000 Joule, while the other still has 23 000 Joule that can used for nothing else but a short and uneventful journey until it falls back to ground (or self destructs).

A heavier HE shell of course can produce more/larger fragments, but the potential of these is fairly low, usually stopped within a few layers of 'stuff' getting in their way. In any case, the KE of the fragments is dependent on the amount and energy of explosives within the shell (from where it gets its source KE), and again has no relation to muzzle velocity or shell weight.

Overall, a HE shells does damage in the following way:

1, Some damage as it enters structure, breaking things on its way, and the damage done equal _the energy required to destroy the particular thing_, the remainder is just _surplus_ *KE* and plays no 'useful' purpose sine the projectile will blow up soon. 
In this regard there won't be too much difference between a high powered and lower power round, because they both possess far greater energy than it is required to penetrate, but this KE will be soon equal to zero as

2, the projectile blows up, and it looses its KE energy. Then it will:
2a, Send small fragments in every direction with very little individual damage capability, but covering a wide area, having enough KE to damage the first light structure/component they hit (lines, wires, skin, crew). This KE is derivied from the amount of explosives in the shell - some part of which is consumed to break up the shell body into fragments. Fragments usually stop in the first thing they hit.

2b, Pressure and hot gases that again comes from the amount of explosives in the shell and will be capable of large amount of damage, quickly diminishing with distance but effecting everything nearby. Now, IIRC the Hispano HEI shell actually contained only half explosives, half incendinaries.

Actually that's why I asked - 'why'. The physics behind it simply don't explain (at least for me) how higher muzzle velocity, or higher projectile weight, can translate into higher damage done, especially as after the projectile blows up initial KE becomes irrelevant and most of the damage is done or directly related the chemical energy from the explosive charge.

Higher muzzle velocity, or higher projectile weight would factor in if we would speak of non-fused, solid rounds (like AP), but even with these there is very little _practical _gain I can see - with penetration figures being in the 20+ mm if armor penetrated region, and most aircraft had 4-6-8-10mm on them at a few vital places, the rest being light structure, easily punctured by any round.



> That doesn’t necessary means that Hisso was better gun, only that the philosophies behind the two guns were slightly different, 151 counted more on blast and numerous small fragments and Hisso more on kinetic energy and fewer but heavier fragments.



Its not different design philosophy - the RAF simply had no other gun than the licensed Hispano, nor did it have M-Geschoss type rounds for it during the war. The French who designed it originally for a single gun installation, which meant that high ballistic performance gun - along with the bulk and recoil of it - in an engine installation, for which it was ideal. And if it was, the British decided after the war for adopting Mine shells into Mauser revolver cannons...

It is noteworthy that the Germans also considered originally a 20mm 'Elephant gun', the 20mm MG C 30 for the Bf 109 but instead opted for lightweight and compact Oerlikons in the wings. All of their later designs were compact with moderate ballistic performance, and Russian designs show similar considerations; it is noteworthy that these weapons were all purpose-designed for aircraft use, rather than adapted pieces originally meant for ground installations, so the designers must have understood that typical fighter combat ranges higher ballistic performance and bulk was less desirable than compactness and high rate of fire.


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## kool kitty89 (Dec 22, 2008)

Kurfurst, if you're comparing the German 20mm "normal" HE shell to the Hispano's, there are some things to note. One reason for the lower weight is that it uses an aluminum fuze (introduced on the MG FF/M) to reduce the recoil closer to that of the Minengeschoss. 

WORLD WAR 2 FIGHTER GUN EFFECTIVENESS
Going by the figures on Tony Williams' site, the German 20 mm HET/HEIT shell carried less than 1/2 the filler of the Hispano's HE shell. (130g HE Hispano 10.4g filler, 115g German HET 3.7g filler)

Also I beleive that the HE or HEI (115 g) shell used by the MG FF/M and MG 151/20 were all tracer types (at least that's the only one listed on Tony Wiliams' site) which explains the small capacity. There was also an unfuzed API round, but that's something of a different nature and the capacity wasn't better than the HET anyway.

The only plain HE shell for the MG 151/20 was the Minengeschoss I beleive, so the Hispano's shells cannot be compared.

However, the old MG FF (not FF/M) used a 134 g HE shell, 4g heavier than the Hispano's (and 6g heavier than the Oerlikon FFF's and FFL's), however I don't know know what the HE content of this shell was. (note this shell apears to be the same as was also used with a few different cartridges and guns like the 20x105B of the MG 204 and the 20x138 flak round)


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## drgondog (Dec 22, 2008)

KrazyKraut said:


> You are forgetting about the two centrally mounted 13mm MGs apparently.
> 
> 1x20mm plus 2x13mm centrally mounted vs. 6x12.7mm is not that different. Given the nature of '44 air combat I'd take the platform with more guns. However i'd take 2x20mm and 2x13mm centrally mounted over both any day.



If you will take the time to read HoHum's post...he said specifically ONE 20mm over P-51D armament.


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## kool kitty89 (Dec 22, 2008)

On the armament of the Bf 109, there were sests with a single, synchronized, MG 151/20 mountd in a pod under the fuselage. This was considered superior to the twin wing pods. (on impact of a/c performance as well as assed weight would be roughly 1/2 and roll rate would not be penalized, and prag would be less)

The reason given for it not reaching service was due to the possibility of mix-up between the electric and non-electric primed ammo for the two guns (the hub cannon being unsynchronized and percussion primed), which doesn't make sense to me, particularly given that both types of MG 151/20 were used together on the Fw 190. (wing root plus outer wing)

A more likely reason is that this configuration elliminated the centerline drop-tank/bomb pylon.

I can't seem to find the original sourse for this, I beleive it was brought up on this forum a while back, maybe Kurfurst knows.


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## drgondog (Dec 22, 2008)

Soren said:


> I think a single .50 cal round would have a very hard time ruining an engine from stern shots, and it wouldn't penetrate the pilots armour AFAIK. The .50 cal round wasn't at all the most destructive of rounds, and it often took alot to down a fighter.
> 
> *I believe you would be wrong about a.) penetrating pilot's armor, and b.) inability to ruin an engine. The reason the SpecWar guys use the Barrett .50 is not only long range sniping but the ability to penetrate > 1/2 steel at 1200 yards to get to an engine. When the circumstances existed that it took a 'lot' of rounds it was usually because a.) not such a great shot or pilot in front is not making it easy - or the ranges start out at 300+ yards and a long ranging chase occurs.
> 
> ...



I think I would prefer two centrally mounted 20's also, particularly the 151/20

The USAF finally figured out better approach to both worlds with the M-61 which puts out the same number of rounds as 10 Ma Duece's, but in 20 mm (or 3000+ in 30mm)


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## kool kitty89 (Dec 22, 2008)

However the performance of the M61 is fairly comperable 4x M39's. Of course the M61 would weigh less than half that of the 4x M39's, though it is fairly bulky by comparison. (and of course requires power feed and spool-up time) The M61A1 is actually slightly less powerful than a battery of 4x M39's. (slightly lower rate of fire, both guns use same ammo)


Somthing that may be significant (or at least a bit odd) is that relatively few modern guns seem to use a Minengeschoss like shell. At least judging by the capacities listed here: Modern Fighter Gun Effectiveness
The exception would seem to be some 30 mm weapons like the ADEN and DEFA, though they still don't seem to manage to pack as much HE as with the WWII 30 mm German shells, even the streamlined ones -wich only hels slightly less filler in any case and much of this was due to the tracer as well. (on possible reason for the lower capacity is the use of significantly shorter -thus smaller- shells than the WWII german ones, so the streamlined fuze takes up proportionally larger space)

And indeed, cut-away pictures of the ADEN shell does look similar to the Minengeschoss.


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## Soren (Dec 22, 2008)

drgondog said:


> I believe you would be wrong about a.) penetrating pilot's armor, and b.) inability to ruin an engine. The reason the SpecWar guys use the Barrett .50 is not only long range sniping but the ability to penetrate > 1/2 steel at 1200 yards to get to an engine.



Maybe, but remember that today we use far better armour piercing projectiles.

AFAIK the WW2 .50cal AP projectile wasn't capable of penetrating the pilots armour of LW fighters. 



> When the circumstances existed that it took a 'lot' of rounds it was usually because a.) not such a great shot or pilot in front is not making it easy - or the ranges start out at 300+ yards and a long ranging chase occurs.



Well considering the amount of rounds fired in one second by the six .50 cals I'd say it usually took a very good amount of rounds to down an enemy fighter.


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## kool kitty89 (Dec 22, 2008)

As to AP capability, remember that the rounds have to go through the aircraft's skin first (and possibly part of the structure) before the armor is reached. The amount of energy lost to the skin will probably not be enough alone to prevent the penetration (depending on the round), but it will probably cause the projectile to tumble. (lighter projectiles will lose proportionally more energy than heavier ones of course)

Also the projectile will probably not be hitling close to perpendicular. (in fact the closer to perpendicular you get, the more fuselage structure you have to go through)


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## HoHun (Dec 23, 2008)

Hi Koolkitty,

>As to AP capability, remember that the rounds have to go through the aircraft's skin first (and possibly part of the structure) before the armor is reached. The amount of energy lost to the skin will probably not be enough alone to prevent the penetration (depending on the round), but it will probably cause the projectile to tumble. (lighter projectiles will lose proportionally more energy than heavier ones of course)

You're right - Tony mentions this effect repeatedly in his books on fighter guns, and it has a dramatical effect on the penetration abilities of armour-piercing rounds.

A report on the Fw 190A-3 prepared by the Oxfordness Research station concludes that in an astern attack, neither 20 mm H.S. A.P., 20 mm H.E./T. (Fuze 253) nor 20 mm S.A.P./I. were able to penetrate the Fw 190's pilot armour when fired from a 10 degree sector after of the plane. The deflection of the projectiles by the aircraft skin and - when it came to the head armour - by the vertical tail was enough to reduce their penetration abilities to a fraction of the nominal value. It was not possible for any of the rounds (including 0.5" A.P.) to penetrate the engine cowling and damage the engine in this type of attack.

With regard to the fuel tanks, the effect you mention is specially stressed:

"The angle of the fuselage with this line of attack is 6 degrees and this gives 0.303" B. Mk.VIII and 0.5" B. Mk.II no chance of causing a fire. These ammunitions will for the most part be deflected or broken up on the 19 s.w.g. fuselage skin; larger angles off tail would make these ammunitions more effective. The detonation of 20 mm. H.E./I. on, or just after, passing through the skin also minimises its chances of producing a fire unless the strike is within 3' of the tank compartment bulkhead."

In fact, 20 mm H.E./I. and S.A.P./I. were the only incendiaries that could damage the tanks at all: "The smaller calibre incendiary ammunitions will either be broken up or deflected away before reaching the fuel tanks."

The RAF definitely had good reasons to leap-frog from 7.7 mm machine guns to 20 mm cannon, skipping the intermediate 12.7 mm calibre. The effectiveness of heavy machine guns for air-to-air combat was not what popular perception today would imagine ...

Regards,

Henning (HoHun)


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## kool kitty89 (Dec 23, 2008)

Wing mounted fuel tanks should be significantly more vulnerable though. 

I'm not sure about the HMG rounds, but the RCMG incnediary bullets (at least the pyrotechnic type) tended to burst on the surface, similar to what you describe. Soren mentioned in the P-47 Fw 190 toughness thread that the German 7.92mm API would tend to leave a 20mm hole due to the explosion of the incendiary. Such rounds would probably scorch anything near the surface, but most wouldn't have the incendary material penetrate far. (the AP penetrator may continue further in API bullets, possibly carrying some remaining incendiary material with it)
Such pyrotechnic rounds do make excellent "spotter" rounds (oftem more useful than tracers in aiming, and without warning the enemy) due to the bright flash upon impact.

White phosphorus incendiaries are something different as they won't explode but rather spread slowly burning fragments all over the place. This will cause any leaking material or fumes that build up to ignite. Some aircraft at high altitude (ie US heavy bombers), after leaving enemy territory and heading home aparently safe would begin to burn when they dropped altitude.

Thermite incendiary is another different possibility as it burns hot enough to cause significant structural damage, it can melt through steel and will literaly cause aluminum to burn (the intense heat plus the added oxidizer -usu Barium Nitrate- of military thermite to the normal iron oxide aluminum powder mix).


Conversely, depending on fuel tank material, non incendiary bullets (AP/SAP, and even Ball) can cause fires by sparking (impact with steel or other components, somtimes magnesium, usually not aluminum).


There's also the guns in the .60 cal/15mm range that are on the verge of being cannons and do have significant HE+Fuze carrying ability.
As well as the upper end of the .50 cal/13mm range like the projectiles of the 13.2mm Hotchkiss and Russian 12.7x108 which seem to have above average filler capacity though still probably not worth fuzing.

And there's the question of developing drawn steel high capacity shells in the .50-.60 cal range. (which should allow in excess of 10% filler to be used, even with fuzing, probably upwards of 15% in the .60 cal's case)


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## Juha (Dec 23, 2008)

Hello HoHun
Quote:” On the other hand, the Il-2 wings were just as vulnerable to mine shells as most, and the wooden wings of the early variants were highly vulnerable because wood responds with rapidly spreading cracks to blast damage that unlike shears in sheet metal consume very little energy as they propagate.”

Yes, and also tail structure was vulnerable to M-Geschoss.

Hello Kurfürst
Now according to Tony’s book page 42 the British Mk 1.z HE shell was expected to blow a hole between 75mm and 200mm in diameter in 12 mm armour plate, have You figures for German HE/HEI? I have somewhere very dark copies of a couple British Hispano ammo tests (I cannot even remember on what kind of ammo, one was probably a comparison of effectiveness of different types of Hisso ammo against certain a/c structures), but not time to dig them out.

Otherwise I agree with Your explanation but “Fragments usually stop in the first thing they hit.” Now that depends, as is case in all hard flying objects, what is the thing and speed, weight, size and shape of the flying object.

Juha

ADDITION:
Quote:” And if it was, the British decided after the war for adopting Mine shells into Mauser revolver cannons...”

Now one tries to match his weapons to potential targets. IIRC RAF was first more interested in 20mm version of MK 213 but then the changed the priority to 30mm version. I’d not be surprised if the main reason of the change and the decision to adopt mine-shell was the emergence of Soviet heavy bombers and Soviet A-bombs.

On Hispano, IMHO RAF was satisfied on it, especially on Mk V, it weighted same as MG 151/20, had a bit higher ROF and higher MV but was a bit longer. And battery on Hissos was perfectly able to made a short work on any German plane they came across up to and incl He 177 if the pilot was able to get a burst or couple in.


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## drgondog (Dec 23, 2008)

kool kitty89 said:


> However the performance of the M61 is fairly comperable 4x M39's. Of course the M61 would weigh less than half that of the 4x M39's, though it is fairly bulky by comparison. (and of course requires power feed and spool-up time) The M61A1 is actually slightly less powerful than a battery of 4x M39's. (slightly lower rate of fire, both guns use same ammo)
> 
> The M61A2 has a slightly higher rate of fire at 6300/minute than the A1 and 50 pounds lighter - but in either case they both add up to 200-400 pounds for feed and storage depending on the ship.
> 
> ...



Noted that the 30x173 on the GAU-8 is at the top of the power list and fires 3900/minute at 3,300 fps.


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## drgondog (Dec 23, 2008)

Soren said:


> Maybe, but remember that today we use far better armour piercing projectiles.
> 
> *We are just recently using up all the WWII and Korean War surplus of 50 Ball and API in Iraq and Afghanistan*
> 
> ...



True, but you see a lot of encounter repoerts in which 100-150 rounds were used to destroy a German fighter - 1.6 to 2.5 sec burst to point of stop shooting.

a six gun battery of .50 HMG did just fine against LW fighters. Go look to the LW records for multiple fighter claims in one sortie against USAAF and look to the number of Ace in a Day records for USAAF versus LW for a single sortie.

Offhand I don't recall one example of 5 US fighters claimed/awarded to LW pilot during a single mission. I could be wrong here but there is no example in Tony Wood's Lists that I have seen so far.

This isn't 'proof' of any kind but makes you think that just maybe the pitiful .50 caliber battery of 4 to six .50's worked very well against the superior armored and armed LW fighter.


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## Soren (Dec 23, 2008)

> We are just recently using up all the WWII and Korean War surplus of 50 Ball and API in Iraq and Afghanistan



Hehe, yes they're used for general use. But against thickly armoured targets we sure don't use WW2 or Korean API rounds, trust me on this one 

Now if you meant against Jeeps trucks, well then the 7.62 will easly ruin the engine as-well. But these aren't armoured and the engines aren't as robust as the 12 cylinder engines used in a/c during WW2. 

I'm not surprised that it sometimes only took 150 rounds to down a fighter. Usually a pilot will bail out of an a/c which he could've otherwise easily brought home just because he knows that there's an enemy behind him ready to shred him to pieces if he proceeds flying. This happened a lot in the late war years with the majority of LW fighters being piloted by rookies.

As for protection, I don't think German fighters were better armoured than Allied fighters in general, I'd say it was similar. The difference was that German fighters were more powerfully armed.


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## Soundbreaker Welch? (Dec 23, 2008)

The P-39 with 6 50. caliber guns and a cannon was pretty well armed. Capable of taking down a few bombers at least on one mission.


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## renrich (Dec 23, 2008)

The fighters designed for WW2 had only one purpose and that was to take a gun or guns into the air and shoot down the other fellow's airplanes. The LW and the Japanese air forces eventually got to the point where their primary concern was shooting down Allied bombers. The USAAF in the ETO fighters were primarily tasked with shooting down LW fighters, mostly single engined. In the Pacific, the USN, Marine and AAF fighters did not have large enemy bombers except for the big flying boats to contend with. The Hellcat, mostly armed with 6-50 cals had a kill ratio of around 15 to 1, shooting down 5257 enemy AC and only losing 270 to enemy AC. The Corsair killed 2155 for 189 losses to enemy air. It seems that those 50 cals were very effective but one could say that some of the Japanes AC were flimsy and their pilots became very poorly trained. In the ETO, the original P51s had four 20mm cannon. When the Merlin P51 came out it mounted four and later six 50cals. The reason for going to the 50 cals may have been because of weight, recoil forces, reliability issues, logistics or other factors. The P51 pilots had to be trained, perhaps on some dusty field in Texas and then put on a ship and sent thousands of miles across the Atlantic along with all their gear to England. Their aircraft likewise along with all the spares and all the maintenance people had to be shipped across the Atlantic. Then all the beans, bullets and other support supplies had to be shipped as long as they were over there. Then those pilots had to get in those cockpits of those P51s that carried those four or six fifties and take those guns several hundred miles into Europe and line them up on LW fighters trying to shoot down bombers and try to prevent them from doing so. During the time they were doing that they destroyed 4239 LW AC while losing 2520 of their own. Those 2520 could have been losses from enemy air, ground fire, engine failure, running out of gas, pilot heart attack or running into rocks in cloud. I don't know if the above statistics could be the result of inexperienced LW pilots or poor equipment but they appear to show that for the mission of taking some guns and flying a long way into enemy territory and decimating the enemy, the P51 with either four or six 50 cals was the best armed fighter.


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## HoHun (Dec 23, 2008)

Hi Soundbreaker,

>The P-39 with 6 50. caliber guns and a cannon was pretty well armed. Capable of taking down a few bombers at least on one mission.

Hm, which P-39 variant had 6x 0.50" guns? I've got manual for the P-39Q here and only 4 are listed.

But don't overestimate that big 37 mm cannon ... it's not particularly impressive, firing a big shell with less explosive content than that of a 30 mm mine shell at a "slow" muzzle velocity of 610 m/s - at a rate of fire of just 2.5 shells per second. 

(Note that the "slow" velocity of the shell would certainly get bashed if the gun were Luftwaffe equipment. As the abovementioned German analysis points out however, this is secondary to other, more important parameters.)

Anyway, here is the direct comparison:

1x 37mm M4 - 30 rpg, 12 s duration - 123 kg - 0,9 MW firepower - firepower per weight: 7,4 kW/kg
1x MK 108 - 60 rpg, 6 s duration - 95 kg - 5 MW firepower - firepower per weight: 52,9 kW/kg

The resulting firepower in relation to selected other fighters:

Ta 152H: 7,6 MW
Me 109K-4: 5,5 MW
Tempest: 4,9 MW
Fw 190A-4: 4,3 MW
Spitfire VC: 2,5 MW
P-47D: 2,3 MW
P-38: 2,2 MW
P-39Q: 2,2 MW
Me 109G-6: 1,8 MW

Nothing to write home about ... though having a central cannon is of course a good thing. I'm not sure about the impact of synchronization on 2 of the 4 12.7 mm guns right now, if I remember they lost quite a bit more rate of fire to synchronization than the electrically primed German guns for example. (Synchronization losses are not considered here.)

Regards,

Henning (HoHun)


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## drgondog (Dec 23, 2008)

Soren said:


> Hehe, yes they're used for general use. But against thickly armoured targets we sure don't use WW2 or Korean API rounds, trust me on this one
> 
> *Trust but verify. The M8 API used in WWII, Korea, etc all the way though Afghanistan is still in use even by snipers using the Barrett M107. The much newer M962 SLAP-T has far greater penetration capability over the M8 API especially against 500 Brinnell hardness. *
> 
> ...



A Mustang had only .4 inch armor plate, I suspect the 109 had thicker but not exactly sure of the composition - but doubt hardened steel comparable to medium/heavy armor.?


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## kool kitty89 (Dec 23, 2008)

Bill, while I agree that the US fighters' armaments were adequate for pretty much all they were used for, I do feel that they would have been more successful with a heavier cannon armament. (or maybe even a gun firing the US .60, though that eneded up as a 20 mm round rather like the 15 mm Maucer round did)

There are a viarety of options for heavier guns that weren't exploited (a .60 cal or 20mm derivative of the Browning or modified Oerlikon FFL, possible the 23mm madsen as a heavier gun) that should have been less problematic to develop than the Hispano. (which was more problematic than it should have been for the US industry)

But this is a topic deserving of its own thread, and probably in the weapons section. (and one that I've been wanting to start, but I'd rather gather some more technical info first)


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## Soren (Dec 23, 2008)

Bill,

Look at the data you provided, the .50 cal API round will penetrate 8mm of vertical standard RHA armor at 1,200m (I suspect they mean 1,200y). That won't do at all against armoured targets, hence why we don't use these against armoured targets. When faced with armoured targets we use sabot rounds.

As for the pilot's armour in the Bf-109, on most models it is a 8mm face hardened steel plate of very good quality.


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## Juha (Dec 24, 2008)

Soren
one could not count that pilot ’s back armour in 109G keep .5 API out, one case when the API went through the back armour and killed the pilot which immediately come into mind is that of L. Otto Fönnekold, 109G-6, WNr. 441931, 31.8.44 at Budak. Only one case but I don’t have info on very many cases in which 109’s back armour was hit by .5 Browning bullets. Other cases of hits which immediately came into mind are one in which the back armour withstood a hit by a Soviet 20mm shell and one in which the stack of aluminium sheets with combined thickness of 22mm, one version of 109G back armour, slowed 2 Soviet 20mm shells or their fragments enough that they stopped inside the fuel tank.

Juha


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## HoHun (Dec 24, 2008)

Hi Koolkitty,

>I agree that the US fighters' armaments were adequate for pretty much all they were used for [...]

"Adequate" - I have often seen this term used in discussions of US WW2 air-to-air weapons, usually to veil the fact that they were outdated and overweight. Sure, the US won the air war anyway, but that doesn't tell us much about the quality of their guns. The RAF won the Battle of Britain with 7.7 mm machine guns ... despite rifle calibre guns being obviously inadequate weaponry.

>I do feel that they would have been more successful with a heavier cannon armament.

If you had suggested to a 1944 Mustang pilot that you could increase his firepower by 50%, give him a centreline battery like the one that made the P-38 such a great firing platform, and get rid of more than 500 lbs of dead weight in his aircraft, it's hard to imagine he'd have declined because his armament was already "adequate". I think it's rather more likely that he'd have enthusiastically accepted your offer, and named his first-born son after you.

The benefits I describe are just what designing the P-51D for a Focke-Wulf-style battery of two wing root cannon would have done for him:

6x ,50 Browning M2 - 400 rpg - 438 kg - 1,7 MW firepower
2x MG 151/20 - 250 rpg - 191 kg - 2,5 MW firepower

That is what technology can do for you ... of course you can win a war with inferior guns, but it will cost you.

Regards,

Henning (HoHun)


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## Glider (Dec 24, 2008)

Or of course, switch back to the 4 x 20mm and make them reliable.


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## Kurfürst (Dec 24, 2008)

Juha said:


> Soren
> one could not count that pilot ’s back armour in 109G keep .5 API out, one case when the API went through the back armour and killed the pilot which immediately come into mind is that of L. Otto Fönnekold, 109G-6, WNr. 441931, 31.8.44 at Budak. Only one case but I don’t have info on very many cases in which 109’s back armour was hit by .5 Browning bullets. Other cases of hits which immediately came into mind are one in which the back armour withstood a hit by a Soviet 20mm shell and one in which the stack of aluminium sheets with combined thickness of 22mm, one version of 109G back armour, slowed 2 Soviet 20mm shells or their fragments enough that they stopped inside the fuel tank.
> 
> Juha



Hmm, test show that you could pretty much rely on that back armor in the 109F/G. The composition was a 8mm back plate, and a 10mm head plate (later variants 10mm head plate with a 60mm armored glass in it). Under the pilots butt there was two pieces of 4mm plates. 

Behind the pilot there was the fuel tank, through which the bullet has to pass through, and slow somewhat further down, and behind the fuel tank there was a large 30 layer dural plate of ca. 22mm thickness as you describe. 

This dural layer was effective in stopping incendinary rounds on its own:

Aircraft Evaluation Report, GERMAN MESSERSCHMITT-109 F, prepered by Materiel Command, Engineering Division, Wright Field, Dayton, Ohio, summarized the results of British firing trials on the effectiveness of the Leichtmetallpanzerung :

_"Additional armor has been found on "109-F" airplanes recently inspected. This is in the form of a laminated dural bulkhead placed approximately 6 inches [152 mm] behind the tank. Total thickness of the thirty laminations used is about 7/8 inches [22,25mm].
The British have carried out tests on one of these bulkheads with the following results : from 100 yards range dead astern, .303 inch and .5 inch incendiary ammunition will not penetrate the dural bulkhead. At this range 20 mm HE/I(high explosive / incendiary ) is still effective in penetrating the bulkhead and ingniting the tank. At 200 yards range, the effect of the interposition of the dural bulkhead is that at 5 degrees off dead astern, .303 A.P. (armor piercing) is completely ineffective against the pilot, but .5 AP in about 30 percent of cases will pass through the bulkhead and will penetrate the 8mm pilot`s armor, even if it has to pass through the tank below fuel level.* Twenty mm A.P. will still be effective in penetrating the pilot`s armor. Subsequent tests reveal that U.S. .50 caliber M1 incendinary ammunition is capable of penetrating the dural plate effectively."_

* This is IIRC a mistranscript from the British report, which stated that in 30% of the cases of hits where the the projectile passed above the fuel line in the test setup to .50 AP could penetrate, but in 70% it couldn't, neither could hits that passed through the fuel tank.

The layered "Leichtmetallpanzerung" was appearantly removed though on late Gs and Ks because space was needed for the 115 liter MW50 booster tank (though some drawings show its still present..), though the light alloy tank and the liquid in it must have offered some ballistic protection as well.

Overall, I would say the pilot was reasonable safe in the Bf 109G from attacks with .50 API from astern at typical combat ranges.


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## Juha (Dec 24, 2008)

Hello Kurfürst
that was what I tried to say but I was not clear enough, I meant that the back protection kept most .5 Browning AP/APIs out but not all so pilot could not trust on that the back armour would safe him, odds were that it could keep single hits out but that wasn't sure. And its a matter of opinion how satisfied one was with the fact that from little under 180m one third of .5 AP hits will penetrate the back armour.

Merry Christmas to all

Juha


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## renrich (Dec 24, 2008)

As mentioned earlier, the P51 came with four wing mounted 20 MMs. Some P51As mounted four 50 cals in the wings and two 50 cals in the nose, firing through the prop arc. The F4U1Cs mounted four 20 mms in the wings. Some late model F4U4Cs mounted the four 20mms. One wonders if the reason why the cannon armed AC did not remain in production was reliability problems and that the reliability problems gradually were solved which was reflected by the F4U4Cs? Another reason the 50 cals could have been favored by the US was that they were almost omnipresent in all US aircraft, ground and sea forces and on all fronts and sticking with them, in spite of a small loss in effectiveness, minimised logistical problems insofar as technicians, ammunition and spare parts were concerned.


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## drgondog (Dec 24, 2008)

Soren said:


> Bill,
> 
> Look at the data you provided, the .50 cal API round will penetrate 8mm of vertical standard RHA armor at 1,200m (I suspect they mean 1,200y). That won't do at all against armoured targets, hence why we don't use these against armoured targets. When faced with armoured targets we use sabot rounds.
> 
> As for the pilot's armour in the Bf-109, on most models it is a 8mm face hardened steel plate of very good quality.



All the figures were given in meters. 

I didn't specify that the M8 API is designed abainst hardened targets I said it would work well against pilot armor, engine blocks, fuel cels, spars, etc, at 200 yards or less. yards. I still say that.

You say it won't?

I say a well aimed burst into the cockpit from any astern angle will shred a luftwaffe protected pilot. You say it won't?

I say the same will destroy a 109 or 190 engine. What say you?

I say the 50 worked just fine against LW fighters. You say what?

I did NOT say a .50 was better than a 20mm. I DID say 6x 50.'s in a P-51D (both M2 and later M3) are preferable to one 20mm 151/20. You agreed IIRC.


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## Clay_Allison (Dec 24, 2008)

The 4 cannon Hurricane was a pretty decently armed bird. They had spitfires with the same four cannnon as well. They were pretty good intercepting both German bombers and their fighter escorts. A 20mm HE round just does a lot more to wreck an airframe than a .50.

Still, I have to give respect to the P-47 with its 8 .50s, seems like you're in a whole new level of power that isn't accounted for by a 33% increase. Watch the gun camera footage and you'll see enemy planes disintegrate when they fall into P-47 gunsights.


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## Glider (Dec 24, 2008)

Juha said:


> Hello Kurfürst
> that was what I tried to say but I was not clear enough, I meant that the back protection kept most .5 Browning AP/APIs out but not all so pilot could not trust on that the back armour would safe him, odds were that it could keep single hits out but that wasn't sure. And its a matter of opinion how satisfied one was with the fact that from little under 180m one third of .5 AP hits will penetrate the back armour.
> 
> Merry Christmas to all
> ...



I admit that I wouldn't be happy with a 30% chance of being drilled and thats assuming that you only get hit by one shell.


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## Soren (Dec 24, 2008)

drgondog said:


> All the figures were given in meters.



True, but since when have the Americans begun to measure in meters 



> I didn't specify that the M8 API is designed abainst hardened targets I said it would work well against pilot armor, engine blocks, fuel cels, spars, etc, at 200 yards or less. yards. I still say that.
> 
> You say it won't?



No, what I'm saying is that the .50cal API round wasn't capable of penetrating the pilots armour in most German fighters at the most common engagement ranges. At 100y tests have apparently shown that 30% will penetrate the 8mm armour plate in the 109, while 70% won't. At >200y I suspect the .50cal API was incapable of penetrating the pilots armour of the 109 190. (The 190 featured 13mm pilots armour)



> I say a well aimed burst into the cockpit from any astern angle will shred a luftwaffe protected pilot. You say it won't?



I say it depends a lot on the range, but in general I'd disagree with you on that note. I think that at a range of over 200y, perhaps 300y, a well aimed burst wont kill the luftwaffe pilot if only hits on the protected areas are achieved. 



> I say the same will destroy a 109 or 190 engine. What say you?



A burst of .50cal rounds will destroy most engines.



> I say the 50 worked just fine against LW fighters. You say what?



I agree, but they could've have mounted a far more efficient armament, like the Hispanos.



> I did NOT say a .50 was better than a 20mm. I DID say 6x 50.'s in a P-51D (both M2 and later M3) are preferable to one 20mm 151/20. You agreed IIRC.



Yes I agree.


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## KrazyKraut (Dec 24, 2008)

Glider said:


> I admit that I wouldn't be happy with a 30% chance of being drilled and thats assuming that you only get hit by one shell.



Wtf it's not like the average fighter had more or better pilot armor. Likewise Spitfire or Mustang pilot armor will have a hard time stopping a 20mm shell so what's your point. Oh right, make axis aircraft look bad by pointing out flaws that are non.


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## Kurfürst (Dec 24, 2008)

Juha said:


> from little under 180m one third of .5 AP hits will penetrate the back armour.[/I]



Hi Juha, and Merry Christmas to you and everyone around in this great discussion board!  

This is not exactly what the report says though, I found the original British one in the meantime, and it says that 30% of those .50 AP rounds will penetrate the pilot backplate which hit above the fuel line in the tank (which is is impossible if the tank is full, and its always full until the droptank is emptied completely). 

IMHO that is pretty good, in fact, as far as stern attacks considered, it seems to be the best protection offered by any WW2 fighter (with the exception of P-39 perhaps, because of rear mounted engine). But you are certainly right is there's no 'certain' protection offered, especially not amongst rather lightly armored WW2 fighters!


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## drgondog (Dec 24, 2008)

Kurfürst said:


> This is not exactly what the report says though, I found the original British one in the meantime, and it says that 30% of those .50 AP rounds will penetrate the pilot backplate which hit above the fuel line in the tank (which is is impossible if the tank is full, and its always full until the droptank is emptied completely).



Kurfurst - is the brit Mk II .5 cal same as M8 API or ball M2?


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## Juha (Dec 24, 2008)

Hello Kurfürst
Thanks for the document. Yes, I also remembered as You indicated in Your earlier message, that the British test results said that .5 didn't have power to penetrate the back armour of the 109F/G if it had to travel through fuel. But on the other hand bullets which travel over aluminium armour usually penetrate the head armour. And probably those that travel through aluminium armour and over the fuel tank had over 50-50 chance to penetrate the back armour. I tried to balance those fact plus added the very small effect of overtaking speed and gave a bit shorter distance than 200y in my analyze.

And 20mm HEI was still effective and would probably ignitite the fuel tank.

I agree that 109F/G had reasonable pilot protection and one could not built an effective WWII era fighter by making it like a tank, one must try to best compromise between protection and weight.

And P-39 had only .25in armour plate to protect the oil tank behind the engine, so even if the pilot might have been well protected from behind, by the way at least in the later versions he also had armour glass head armour, I cannot say was that German or Soviet innovation, the plane wasn't very well protected against attack behind. I have not time to check the protection afforded by US fighters so I don't have opinion on 109's protection vs other fighters.

Juha


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## Glider (Dec 24, 2008)

KrazyKraut said:


> Wtf it's not like the average fighter had more or better pilot armor. Likewise Spitfire or Mustang pilot armor will have a hard time stopping a 20mm shell so what's your point. Oh right, make axis aircraft look bad by pointing out flaws that are non.



Lummy you are touchy. Can I ask if you would feel comfortable about being in a seat with a 30% chance of being drilled?
Did I say that a Spit or a P51 or any other aircraft was better protected, or would stand a better chance? I don't think so.

I certainly get the feeling that some people have the opinion that I am almost a rabid anti German poster but this is simply not true. Look at the postings I have made on the technology thread, or any thread about which is the best fighter in the early war period where I have always gone for the 109. Or any thread that the German Type XXI submarine has been mentioned.

In this thread there are some things that I don't understand and when I have asked questions have not been answered. Basically they are:-

1) I do not believe that the Mk108 was a good long ranged weapon. Soren has said it was and he has the pilot reports to prove it. I am happy to change my views; all I have asked is where I can read these reports. His posting showed a drop of 31meters at 1000 meters and in my book that isn't good. Henning’s posting showed the effectiveness falling off a cliff after 500m which tends to support my view. Unfortunately Soren has not given me any clue as to where those reports are, he has just gone silent on that point.
2) I happen to believe that 4 x 20mm Mk V guns in the nose is a better set up than the Ta152. This is seen as sacrilege but you have 4 guns which are concentrated in the nose capable of long range fire with an excellent rate of fire. I concede (and always have) that the Ta152 may have more raw firepower and the guns are concentrated. However the sights on the Ta152 will be set up as a compromise meaning that you will not get the best out of each weapon as the ballistics are so different. On the Meteor the sight will be set up for the one gun and the fire more concentrated. I am not insisting that I am right or that everyone should agree with me, but it is a valid case. 
3) The power ratings for each weapon I don't understand. I have asked how they were calculated and was put on an ignore list. It was a reasonable question. Tony Williams who is an expert in these matters has a different set of figures and the normal measure in the real world is K Joules or ft pounds. I have never seen the measure that Henning uses.
I do know something about ballistics have done target shooting for a number of years as well as taking coaching / instruction courses and until three years ago was an instructor which isn't that common in the UK outside the armed forces. The one thing I have learnt over the years is that i don't know everything and have concentrated on small arms, but I do know enough to feel that I can ask a question if i see something new.
Again I must emphasise that I am not saying that Henning is wrong, but I do get a little worried that when I ask for an explanation, I get put on an ignore list.


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## Soren (Dec 25, 2008)

Don't feel bad about Hennings ignore list Glider, he is very quick to place you there, heck I'm on it too 

As for the reports, I'll dig'em up for you. I remember reading about LW pilots lopping 30mm shells at the bombers from over 1,000m away, with good results. And when you think about it then it's really quite logical, you simply aim at what would be 31m above the target at 1,000m. And the 30mm shell, being as stable as it is, will hit very closely within the horizontal aimpoint at 1,000m.


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## kool kitty89 (Dec 25, 2008)

A comment on the armor issue. In the P-39's case, from what I've read the armored glass head armor was a Russian modification, with standard US aircraft either having armor plate, or no head armor.

I also beleive the Bf 109's fitted with the "Galland Hood" used armored glass in leu of plate to better take advantage of the increased rear visibility.


Henning,


HoHun said:


> Hi Koolkitty,
> 
> >I agree that the US fighters' armaments were adequate for pretty much all they were used for [...]
> 
> ...



I pretty much agree, though given the continuing problems with US production of the Hispano and lack of a back-up they didn't realy have an alternative. (though _at least _they already had a decent aircraft HMG in wide used, unlike the RAF, had the Hispano been a failure for them they'd have been in bigger trouble)


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## Juha (Dec 25, 2008)

Hello KK
at least some P-39s seemed to have armour glass head armour installed already at factory, but the idea might well have been orginated from Soviets.

Juha


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## HoHun (Dec 25, 2008)

Hi Koolkitty,

>Henning,

Hm, could you use a different quotation style please? As the forum engine excludes quoted content from the answer's quote, I get almost none of your text into the editor field. I have to go back and copy it manually via the clipboard, and as you don't have used any signal characters such as ">" at the beginning of a line, this still leaves me confused about which bits were written by whom, so I have to go back and copy your text paragraph by paragaph. (And all-bold paragraphs are ugly to the eye, too.)

>What I meant is that, for the most part, the armament they had were "good engough" for most of the missions they flew.

Being 500 lbs overweight because the 12.7 mm Browning and its ammunition is twice as heavy as a contemporary 20 mm cannon has a negative impact on your aircraft's performance and thus on your operational success. 

500 lbs is about the weight of the Gustav's gondola weapons, which in popular perception turned a nimble fighter into an iron dog. The same amount of weight doesn't suddenly become irrelevant if it's added to an aircraft marked with a star instead of a cross.

>Also there were other things about the P-38 that made it a good gun platform, the nose open for armament without prop or engine in the way, the large size and weight to better absorb recoil, the couterrotating props eliminating torq.

The reduction of firepower of a synchronized MG 151/20 was just around 5 % with electrical synchronization. As I have pointed out above, the benefit of centreline fire was worth a multiple of that due to the better hit ratio. The Focke-Wulf with its wing root cannon was a great firing platform without needing the size and weight of the P-38, and the counterrotating propellers were noted to induce yaw after each power change because the engines did not reach exactly the same power settings in practice, requiring re-trimming by the pilot every time. Not to say the P-38 wasn't a great firing platform ... but the primary reason was just that it offered centreline fire.

>In this same vein, mounting a hispano on the centerline of the P-51 would have been impossible without modification to the gun to allow synchronization (ie electric priming or an independent firing pin) or modification to the engine design to allow an engine mounted gun.

Certainly - I don't say that it was a realistic suggestion in 1944 to equip the P-51D with two wingroot 20 mm cannon. I have just highlighted the advantages to show that the 12.7 mm machine gun armament was overweight, far behind the state of the art, and detrimental to the flight performance of the USAAF fighters.

It's obvious that the USAAF won the air war over Germany, but it's similarly obvious that the USAAF did so with rather poor barrel weaponry. I'm sure you'll have no problem to get the former acknowledged by everyone here on this forum, but pointing out the latter is guaranteed to touch off a frenzy of spin-doctoring ...

Regards,

Henning (HoHun)


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## drgondog (Dec 25, 2008)

Juha said:


> Hello Kurfürst
> Thanks for the document. Yes, I also remembered as You indicated in Your earlier message, that the British test results said that .5 didn't have power to penetrate the back armour of the 109F/G if it had to travel through fuel. But on the other hand bullets which travel over aluminium armour usually penetrate the head armour. And probably those that travel through aluminium armour and over the fuel tank had over 50-50 chance to penetrate the back armour. I tried to balance those fact plus added the very small effect of overtaking speed and gave a bit shorter distance than 200y in my analyze.
> 
> And 20mm HEI was still effective and would probably ignitite the fuel tank.
> ...



Juha - I have to dig but the 109 definitely had better protection aft than either the 51, 47 or 38. IIRC each of the US Fighters had .25 to .40 inch thick armor on seat back. Mustang definitely had zero armor behind the fuselage fuel tank.


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## drgondog (Dec 25, 2008)

Glider said:


> Lummy you are touchy. Can I ask if you would feel comfortable about being in a seat with a 30% chance of being drilled?
> Did I say that a Spit or a P51 or any other aircraft was better protected, or would stand a better chance? I don't think so.
> 
> I certainly get the feeling that some people have the opinion that I am almost a rabid anti German poster but this is simply not true. Look at the postings I have made on the technology thread, or any thread about which is the best fighter in the early war period where I have always gone for the 109. Or any thread that the German Type XXI submarine has been mentioned.
> ...



Very articulate summary Glider. Great post.


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## renrich (Dec 25, 2008)

Hmmmmmm, Re. " the 12.7 Browning and it's ammunition is twice as heavy as a contemporary 20 mm cannon," my source on US AC guns for WW2 has the 50 cal gun weighing 70 pounds and 54 inches long. Weight of belted ammo is .30-.311 pounds per round depending on AP or tracer. The 20 mm weighs 129 pounds and is 78 inches long. The belted ammo ranges from .54-.616-.766 pounds depending on explosive or tracer. Consequently, six fifties would weigh 420 pounds and four 20mms would weigh 516 pounds plus the additional weight for ammo. Perhaps some 20 mms were available outside the US which were lighter. The 20 mm in the A6M weighed 82.83 pounds(still more than the 50cal) but had a lower rate of fire and much lower MV than the US 20mm. The F4F3 mounted four 50 cals with around 400 rds per gun which was plenty as far as Navy pilots were concerned. The F4F4 only went to six guns with reduced rds per gun because the British insisted on it. Late F4F4s , as well as the FM2s went back to 4- 50s which was plenty adequate against Japanese AC and the occasional FW Kondor or JU88. Of course the above info which seems to contradict some other posts probably won't count as I am on the ignore list.


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## drgondog (Dec 25, 2008)

HoHun said:


> >What I meant is that, for the most part, the armament they had were "good engough" for most of the missions they flew.
> 
> Being 500 lbs overweight because the 12.7 mm Browning and its ammunition is twice as heavy as a contemporary 20 mm cannon has a negative impact on your aircraft's performance and thus on your operational success.
> 
> ...



I have talked to quite a few German pilots who absolutely agree that things probably would have been worse had the Mustang and Thunderbolt been equipped with 20mm versus .50 cal. None of them expressed joy that they were 'only' confronted with .50 caliber.

A lot of ammo of .50 caliber seems to have worked in the context of taking out many multiple scores of 3 and above per sortie versus the LW so it wasn't the detrimental condition you suggest...


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## claidemore (Dec 25, 2008)

One important factor being overlooked is firing time. 
For example:
P51A, with 4x20mm has firing time of 12.5 seconds. 
P51B/C- 4x.50 has firing time of 23/24 seconds. 

Given the low hit probability of -10 % in WWII, on a long range mission over enemy territory, double the firing time is a good thing. 

The Spitfire Mk XVI and Mk XIVE with 2x20mm and 2x.50 were highly rated by the pilots who used them, particularly against ground targets. Firing times of 20 seconds for the .50s and 13 seconds for the 20mm. An excellent compromise of extended firing time and long range capability (.50s) with destructive power (20mm Hispano).


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## HoHun (Dec 25, 2008)

Hi Claidemore,

>One important factor being overlooked is firing time. 

I don't think it has been overlooked - remember the "muzzle loader effect"?

Firing time is meaningless by itself - the question is how much damage you can do with the ammunition supply you carry.

Though I have already addressed it once, it seems I have to repeat it here: Cannon armament does not translate into a smaller ammunition supply.

This erroneous conclusion is based on the comparison of firing times, which of course is inaccurate - 20 shot are 20 shot, and if you're firing them from a muzzle loader, you don't have any advantage over a guy who's firing them from an assault rifle just because it takes you longer to do so.

Everything else the same, long firing time (or "ammo duration", as it's sometimes put) simply equates to "poor firepower", as illustrated by the muzzle loader example.

Here is a comparison of the mass efficiency of various rounds, showing mass of the complete cartridge (including belting) in relation to the total muzzle energy (kinetic plus chemical, typical mix):

MK 108 (30x90RB): 860 kJ/kg
MK 103 (30x184B): 634 kJ/kg
MG 151/20 (MX) (20x82): 547 kJ/kg
MG 151/20 (20x82): 494 kJ/kg
Hispano II (20x110): 432 kJ/kg
MG-FF (20x80RB): 288 kJ/kg
MG 151 (15x96): 201 kJ/kg
,50 Browning M2 (12,7x99): 198 kJ/kg
MG 131 (13x64B): 180 kJ/kg
MG 17 (7,92x57): 147 kJ/kg
Browning ,303 (7,7x56R): 146 kJ/kg

So the Hispano ammunition is more than twice as effective per unit of weight than the 12.7 mm Browning ammunition, and the MG 151/20 ammunition about 2.5 times as effective.

The MG FF looks a bit inefficient in this comparison due to the inclusion of the weight of the drums, which means that it is not entirely comparable since belt-fed guns required ammunition boxes that were not considered in this comparison. However, leaving out the weight of the drums would make the MG FF look artificially good, so that's no solution either.

30 mm cannon further increase their weight efficiency, with the high-velocity MK 103 projectiles being three times as effective per unit of weight than the 12.7 mm Browning, and the MK 108 projectiles even four times as effective.

Regards,

Henning (HoHun)


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## lesofprimus (Dec 25, 2008)

Good stuff here fellas...


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## Glider (Dec 25, 2008)

HoHun said:


> Hi Claidemore,
> 
> >One important factor being overlooked is firing time.
> 
> ...


I must disagree with this assumption. What matters in particular in air combat where you are only likely to have about two seconds to fire, is how much damage you can do in those two seconds. This of course relates to firpower.
What also matters is how long you can keep firing which relates to the amount of ammunition that you carry.
The Whirlwind is a classic example, in its time with 4 x 20mm in the nose it had almost unmatched firepower. However it only had 6 seconds of ammunition.
The Muzzle loader example has very poor firepower but a long duration.




> Here is a comparison of the mass efficiency of various rounds, showing mass of the complete cartridge (including belting) in relation to the total muzzle energy (kinetic plus chemical, typical mix):


This is the bit that I feel needs explanation as Muzzle Energy has nothing to do with Chemical Energy. Unless we know how you get from the real Muzzle Energy Figures to *these figures you quote which are NOT Muzzle Energy*, there must be a question mark.

I invite anyone to do a search and find out the definition of Muzzle Energy.


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## lesofprimus (Dec 25, 2008)

Muzzle energy is the kinetic energy of a bullet as it is expelled from the muzzle of a firearm. It is often used as a rough indication of the destructive potential of a given firearm or load. The heavier the bullet and the faster it moves, the higher its muzzle energy and the more damage it will do.

The general formula for the kinetic energy is:

E = 0.5 • m • v2 
In SI units, mass m is in kilograms and velocity v is in metres per second, giving kinetic energy E in joules.

When using a system of units that is not self-consistent, or if the weight of the bullet is used rather than the mass, a conversion factor must be added. For example, to get muzzle energy E in foot-pound force, where

v is the velocity of bullet (in feet per second) 
m is the mass of bullet (in grains) 
the formula is

E = m • v2 / (2 • 32.1739 • 7000). 
Most sporting arms publications within the United States report muzzle energies in foot-pound force, and, when publishing kinetic energy tables for small arms ammunition, use a dimensional constant of 32.163 lbm • ft / lbf • s² rather than the standard acceleration of gravity of 32.1739 ft / s².

The bullet energy, remaining energy, down range energy and impact energy of a projectile may also be calculated using the above equations.


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## HoHun (Dec 25, 2008)

Hi Les,

>Muzzle energy is the kinetic energy of a bullet as it is expelled from the muzzle of a firearm. 

Note: as pointed out above, I considered the total muzzle energy (kinetic plus chemical, typical mix). As the point in firing shells is to increase destructive power far beyond what would be possible on kinetic energy alone, it doesn't make sense to limit the consideration to kinetic energy alone.

To compare total muzzle energy is indeed flattering for projectiles that rely mostly on kinetical energy ... here is a comparison of downrange speeds:


```
Weapon                      v0  v400   v_av   T400
12.7 mm AP M2 (36" Barrel) 867   680  773,5   0,52 <- 12.7 mm Browning M2
20 mm API (from AP M75)    750   555  652,5   0,61 <- 20 mm Hispano II
20 mm mine shell           805   424  614,5   0,65 <- MG 151/20

Speeds in m/s, Time to 400 m in s
```

In terms of total muzzle energy, this yields (figures are approximates as I don't have full details on each ammunition type):


```
Weapon                        E0   E400 E400 %
12.7 mm AP M2 (36" Barrel)  21.0   14.7   70 % <- 12.7 mm Browning M2
20 mm API (from AP M75)     94.7   78.1   83 % <- 20 mm Hispano II
20 mm mine shell           142.9  121.3   85 % <- MG 151/20

Energies in kJ, percentage downrange in relation to full energy at the muzzle.
```

Regards,

Henning (HoHun)


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## claidemore (Dec 25, 2008)

HoHun said:


> Hi Claidemore,
> 
> >One important factor being overlooked is firing time.
> 
> ...



I don't think the comparison of a muzzle loader ( 3 rpm) to an assault rifle (600 rpm?) has any relevance to a comparison of a 600 rpm cannon to a 800 rpm heavy machine gun. Firing time is important for similar rates of fire and the muzzleloader example is misleading. 

Remember the 9-5% hit ratio? Double the firing time and you double the number of hits. Plus the shooter has twice as much time to learn from his mistakes and increase his accuracy. 

The question is not which round produced more damage, but whether or not a certain round produced 'enough' damage. As drgondog pointed out, the 4x.50s and 6x.50s in the varous Mustang models certainly produced 'enough' damage. 

USN pilots bemoaned the change from 4x.50s to 6x.50s because of the reduced firing time. While the 'brass' wanted more destructive capability, the pilots wanted more firing time. Every soldier wants more firing time (no matter what the rate of fire). 

Canon armament vs HMG or LMG, given a limited amount of space on a given airframe for storage of ammunition will definately translate into a smaller ammunition supply, (fewer rounds). The E wing Spitfire for example carried 135 x 20mm rounds and 356 x .50 rounds, compared to 120 rds per gun in a twin 20mm 'C' wing. Those 2 x20mm cannons may be more effective or efficient, but there are definately fewer rounds and reduced firing time.

That being said, and at the risk of ambivalence, I believe that the 4 x 20mm armament is a better choice than the 6 or 8 x.50s.


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## Glider (Dec 25, 2008)

The definition suppplied by Les is of course correct and its normal in millitary applications to multiply this by the rate of fire for a second and arrive at a figure per second.

This is a rough and ready figure as Henning would agree, as the explosive content should be catered for in some way but there is no agreed standard for this. I do not pretend to have the best solution. 
Tony Williams on his site explains how he caters for such additional energy and if you wish to disagree with him then he has explained how his figures work on which you can base a case. Full marks to him
Re Hennings figures the $24000 question is how does he calculate the Chemical Energy and build it into his figures? 

Tony is an expert who has devoted a lot of time and effort on this topic and unless there is an explanation as to how Henning calculates his numbers then people may want to consider both solutions as the differences in some cases are quite significant.

To use the often quoted 
1 x 20mm Mk151 and 2 x 13mm HMG Tony gives a factor of 288
6 x 0.5 HMG Tony gives a factor of 360


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## Kurfürst (Dec 25, 2008)

Energy content of different kind of explosives can be relatively easily found in specific books.

As for Tony's calculation of projectile 'power', it is a simple approach and Tony readily admits it may not be perfect one but rather an educated guess if I recall his explanation in his article correctly. It needs to be understood that it is a very complex subject with an insane amount of variables, especially with regards what structure the projectile hits.

The most severe flaw of Tony's calculation of KE and CE total of the projectile is that it derieves CE from existing KE - but there's simply no corellation between the two! To use a simple example, how much greater is the explosion from a hand granade if I throw it away than if I hold it in my hand? 

In Tony's way calculation, the hand granade would be more destructive the faster I throw it (but we all know that if I throw at and hit someone with a hand granade, 99% of the damage he will get will be not from being hit with a relatively heavy object, fast moving object - KE -, but the fact it blows up, tearing his head off!). OTOH, in Tony's calculation I can safely hold a hand granade in my hand until it blows up, it will do zero damage (at least in this theory) because, well, its KE is also zero..!


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## HoHun (Dec 25, 2008)

Hi Claidemore,

>Remember the 9-5% hit ratio? Double the firing time and you double the number of hits. 

Hm, you implicitely assume that when you double the firing time, the number of firing opportunities obligingly doubles itself, too. This is not a given, and actually the reason why firepower is important at all.

Ask yourself why the USAAF fighters carried six to eight guns instead of just one or two ... here are two batteries of equal weight:

8x ,50 Browning M2 - 390 rpg, 30 s duration - 575 kg - 2,3 MW firepower
1x ,50 Browning M2 - 4965 rpg, 382 s duration - 575 kg - 0,3 MW firepower

So why is the first battery better suited for air-to-air combat then the second battery, which has more than 12 times the firing duration?

>The question is not which round produced more damage, but whether or not a certain round produced 'enough' damage. As drgondog pointed out, the 4x.50s and 6x.50s in the varous Mustang models certainly produced 'enough' damage. 

Firepower is a continuous value, and more is better. I have not seen any historical report on WW2 firepower that uses the term "enough", and to be honest, it sounds just like the kind of "peacock term" that one would use to gloss over inconvenient facts. See also: Wikipedia:Avoid peacock terms - Wikipedia, the free encyclopedia

>USN pilots bemoaned the change from 4x.50s to 6x.50s because of the reduced firing time. 

Hm, you must be thinking of the armament upgrade from the F4F-3 to the F4F-4 which was discussed in detail in another thread on this forum. I'm sure that if it hadn't resulted in an considerable weight increase of the F4F-4, only part of which was owed to the increased armament, it would have been received much better. In fact, this example highlights the importance of weight as a factor - and the problem with the 12.7 mm machine gun batteries, regardless of the number of barrels that were actually used, was that they were much heavier than the contemporary state-of-the-art.

>Canon armament vs HMG or LMG, given a limited amount of space on a given airframe for storage of ammunition will definately translate into a smaller ammunition supply, (fewer rounds).

Do you have actual figures on the volume per round for cannon versus heavy machine-gun rounds? I might be able to provide some figures for German ammunition ...

With regard to weight, there is no question that cannon ammunition is a great deal more efficient than machine gun ammunition. Here is a comparison of the mass efficiency of various rounds, showing mass of the complete cartridge (including belting) in relation to the total muzzle energy (kinetic plus chemical, typical mix):

MK 108 (30x90RB): 860 kJ/kg
MK 103 (30x184B): 634 kJ/kg
MG 151/20 (MX) (20x82): 547 kJ/kg
MG 151/20 (20x82): 494 kJ/kg
Hispano II (20x110): 432 kJ/kg
MG-FF (20x80RB): 288 kJ/kg
MG 151 (15x96): 201 kJ/kg
,50 Browning M2 (12,7x99): 198 kJ/kg
MG 131 (13x64B): 180 kJ/kg
MG 17 (7,92x57): 147 kJ/kg
Browning ,303 (7,7x56R): 146 kJ/kg

This energy efficiency has direct bearing on your above statement on the 9-5 % hit ratio: You can calculate the energy of the ammunition supply of a certain fighter, then multiply it by your assumed hit ratio - and you have the amount of destructive energy applied to the target if all ammunition is used up.

Note that firing duration, rate of fire, firepower etc. do not even enter this equation.

Here some examples:

8x ,50 Browning M2 - 390 rpg, 30 s duration - 343 kg ammunition, 67,9 MJ total
1x ,50 Browning M2 - 4965 rpg, 382 s duration - 546 kg ammunition, 108 MJ total
2x MG 151/20 - 250 rpg, 21 s duration - 107 kg ammunition, 52,9 MJ total
2x MG 131 - 475 rpg, 32 s duration - 74 kg ammunition, 13,3 MJ total

You can see that the ammunition supply for the P-47D is good for 67,9 MJ total energy, with 9-5 % of that being brought to bear upon the target if all of it is fired off during a mission.

The Fw 190D-9 has a total ammunition supply of 66,2 MJ total energy, with the same 9-5 % being brought to bear if all is fired off.

(Note that the Thunderbolt's ammunition weighs 343 kg while the equivalent Focke-Wulf ammunition weighs only 181 kg.)

The firepower comparison is telling:

Fw 190D-9: 3,0 MW
P-47D: 2,3 MW

Same amount of ammunition, the P-47 has lower firepower and thus the longer firing duration. The "muzzle loader effect" is in fact evident here, but of course with realistic rates of fire it is not as dramatic as in my musket-vs.-assault-gun example, which was just meant to demonstrate the principle.

>That being said, and at the risk of ambivalence, I believe that the 4 x 20mm armament is a better choice than the 6 or 8 x.50s.

Quite clearly, and by a considerable factor:

Tempest: 4,9 MW
Typhoon: 4,2 MW
P-47D: 2,3 MW
P-51D: 1,7 MW
P-51C: 1,1 MW

I don't expect anyone will contradict that part of your assessment 

Regards,

Henning (HoHun)


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## Juha (Dec 25, 2008)

Kurfürst
IMHO Your hand grenade metaphor isn’t very good because we are talking on guns. IMHO nearest to a shell with zero kinetic energy is one which exploded in a gun chamber or in its ammo tray and its effect to enemy is nil. And how you value Japanese Ho-301 40 mm cannon with high rate of fire but with very low MV? MV has its role when we valued a/c armaments.

Juha


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## Juha (Dec 25, 2008)

HoHun
IIRC the reduction of firing time with F4F-4 introduction to service was a major complain among USN pilots according to Lundstrom's excellent "The First Team". Pilots saw 4*.5 HMG as adequate armament against Japanese a/c and saw also that after you had run out ammo your chances to help the defence of your flat-top or your charges was minimal. And without flat-top... Simple as that.

Juha


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## Burmese Bandit (Dec 25, 2008)

Summary of debate: .50 caliber very good, 20 mm world beater, mustang with 2 20 mm and 2 .50 caliber would have won the war by Christmas 1944...

(exaggerated - don't take me literally! - but you get my drift...)


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## HoHun (Dec 25, 2008)

Hi Juha,

>IMHO Your hand grenade metaphor isn’t very good because we are talking on guns.

It was a deliberately extreme example to highlight the shortcomings of Tony's approach.

With regard to guns, you'll see that in Tony's table the 30 mm shell of the MK 103 has almost twice the power of the same shell when fired from the MK 108. If it would be - for example on a firing range - be placed in a dummy target fuselage and detonated there, Tony's formula would give it zero power since the shell is at rest.

Here is the comparison:

```
Cartridge   V0   Weight  % HE    Power   Energy
30x184B    860      330    25       99      583
30x90RB    505      330    25       58      503
30 v=0       0      330    25        0      461

v0 [m/s], Weight [g], Power "Tony Index", Energy [kJ]
```

You can see that even at rest, the 30 mm shell has a very high energy content (82.5 g explosives going off ...), and that the energy gain the round has from being fired at a high muzzle velocity is nowhere near the twofold increase you'd assume from Tony's power figure.

Regards,

Henning (HoHun)


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## Juha (Dec 25, 2008)

Hello HoHun
with all respects, Tony is comparing guns not shells. How you hit anything with with MV 0 m/s? What is the effect of a miss?

What is your opinion on Ho-301? How effective it was according to Your formula?

Juha


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## HoHun (Dec 25, 2008)

Hi Juha,

>with all respects, Tony is comparing guns not shells. 

Hm, check out his site:

WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

See TABLE 1: CARTRIDGE DESTRUCTIVENESS ... Tony is comparing shells (and other projectiles) in preparation for the next step, comparison of guns in TABLE 2: GUN POWER AND EFFICIENCY.

Note that gun power is simply a multiplication of rate of fire and cartridge power in Tony's table - the power of the cartridge directly determines the power of the gun.

>How you hit anything with with MV 0 m/s?

The point about the "0 m/s" 30 mm mine shell is that it is still highly destructive, while Tony's formula gives it a power of zero. This proves that Tony's formula gives a nonsense answer when estimating the power of explosives as a charge of 82.5 g going off in a single or twin-engined aircraft will usually destroy it. (Luftfahrt International 7 shows pictures of the effect of 60 to 100 g charges gone off inside aircraft wings and fuselages ...)

>What is your opinion on Ho-301? How effective it was according to Your formula?

The fourth table on Tony's page shows that my calculation for the effectiveness of the Ho-301 yields an increase by a factor of 2.36 as his formula tends to underestimate the effect of slow explosive shells.

In absolute terms, the Ho-301 shell compares unfavourably to the MK 108 as it only contains 50.9 g explosives to the MK 108's 82.5 g, and the rate of fire is lower too.

MK 108 - 5,0 MW firepower
Ho-301 - 2,3 MW firepower

Additionally, the weight of the Ho-301 and its ammunition is much higher, though I don't have exact figures including belting. Accordingly, the MK 108 is a much better weapon than the Ho-301.

Regards,

Henning (HoHun)


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## Kurfürst (Dec 26, 2008)

Juha said:


> IMHO Your hand grenade metaphor isn’t very good because we are talking on guns. IMHO nearest to a shell with zero kinetic energy is one which exploded in a gun chamber or in its ammo tray and its effect to enemy is nil.



It is very hard to misunderstand why I brought up this example...  
But here's the moral of it: kinetic energy does not factor into the chemical energy of the shell (the first is decreasing, and at typical combat distance its about 1/2 than what was it at the muzzle, the latter is constant regardless of range)



Juha said:


> And how you value Japanese Ho-301 40 mm cannon with high rate of fire but with very low MV? MV has its role when we valued a/c armaments.
> 
> Juha



IMHO hit probability should be factored in into the total level of potential destruction done to the target, which you can break down to two components, time to target (better with high Mv) and dispersion/concentration of firepower (usually worse with high Mv and wing armaments).

Several models should be used, ie. a large bomber sized target travelling straight and level, and a fighter sized target doing maximum sustained/and maximum-g turn at a common firing distance of ca 200m. The calculated chance of hit for these different targets can be used as a multiplier for the total destructive_ potential _of projectiles, and this can be expressed in various terms - no. of projectiles need to be expanded, time of steady fire solution required. This is pretty much that German reports approach the subject. But this is an increadibly complex and challanging simulation - it may be _too tempting_ to HoHun as matter of fact, and he may actually go as far as doing it! 8) 

I don't consider Tony's approach scientific, or accurate. Its however a good educated guess based on an unscientific rule of thumb method, and it gives results that match real world observations in most cases; however, the method quite clearly understates the effect of HE shells.

And like I said, there's also an immense number of factors with regarding well the shell may hit. AP hitting the wingtip will just pass harmlessly through, but AP or HE fragment hitting the pilot brings down the plane with a single round.


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## Timppa (Dec 26, 2008)

Kurfürst said:


> .
> As for Tony's calculation of projectile 'power', it is a simple approach and Tony readily admits it may not be perfect one but rather an educated guess if I recall his explanation in his article correctly. It needs to be understood that it is a very complex subject with an insane amount of variables, especially with regards what structure the projectile hits.
> .



I agree. IMO the projectile power topic is one of those where it is is impossible to find the 'right' answer. While Tonys approach is simplistic (and incorrect when v=0) it gives results quite close to real world observations at realistic impact speeds.

HoHuns approach is also simple and logical, and stresses the explosive effect.

But even the Luftwaffe did not try to maximise the explosive effect in their ammunition belting, otherwise they would have used only, or mostly mine grenades. According the 'Schiessfibel' only one third of MG151 ammo was Mine, other were incendiary or AP rounds with no explosive effect whatsoever. This was against the hardest targets, 4 engined bombers (against other aircraft it was 3 mines out of 5). MK108 mix was half Mine and half incendiary (the latter also without explosives).


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## renrich (Dec 26, 2008)

Ammo load can be a major factor in a battle. An example is in an article recently published, I think, by a Japanese studying the Midway Battle. The A6M carried only 60 rounds per gun for the 2-20mms in the wings. The two rifle caliber Mgs in the nose carried a lot of ammo but were not terribly effective against the US AC. During the period between the recovery of the Japanese first strike against Midway and the rearming of a strike to be launched against the US CVs, the attacks against the IJN CVs by land and carrier based air kept the IJN fight decks tied up in recovering, rearming and relaunching the A6Ms in the CAP that were running short of cannon rounds. Consequently, the strike force meant for the US CVs had to be kept below on the hangar deck until the flight deck was clear. It took about an hour to get a full strike up to the flight deck and launched, partly because the engines could not be started and warmed up on the hangar deck of IJN CVs. My guess is that the IJN pilots and admirals would have traded those two 20 mms in the wings for a pair of 50 BMGs with several hundred rds of ammo each during that battle.


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## HoHun (Dec 26, 2008)

Hi Timppa,

>While Tonys approach is simplistic (and incorrect when v=0) it gives results quite close to real world observations at realistic impact speeds.

Hm, I don't think he has validated his rule of thumb. If we consider it realistic in the middle of the velocity band, which I think is a reasonable assumption, his table 4 shows that in fact the most serious differences between rule of thumb and energy approach are for guns that fall out of the middle of the speed band, such as the Ho-301 and the MK 108. For other guns, the high-explosive rounds get under-valued by Tony's formula while the armour-piercing rounds get overrated, so that in the mix the differences more or less even out - which maybe helps to justify the rule of thumb.

>HoHuns approach is also simple and logical, and stresses the explosive effect.

In fact, my approach treats all kinds of energy equal and does not particularly stress the explosive effect. If you meant to stress to contrast to Tony's formula which neglects the explosive effect a bit, then I'd of course agree 

>According the 'Schiessfibel' only one third of MG151 ammo was Mine, other were incendiary or AP rounds with no explosive effect whatsoever. This was against the hardest targets, 4 engined bombers (against other aircraft it was 3 mines out of 5). MK108 mix was half Mine and half incendiary (the latter also without explosives).

That's right. I did in fact base my analysis on Tony's data because he's an accepted source, knowing well that there are detail differences to other sources I have - partially because the ammunition often came in different variants. If I'd use my source data, some German weapons would look better, others would look worse than with Tony's data. (It's not limited to German guns - as Tony only gave data on the API for the 12.7 mm M2 Browning, which historically was the most effective ammunition, I have based my estimate on a pure API belting. The Hispano II was historically used with a share of ball ammunition untill 1942, but I'm basing my calculation on the more effective HE and AP projectiles Tony provided the data for.)

The 1:3 mine shell mix against bombers against the 3:5 mine shell mix against all other aircraft is consistent with the trials published in Luftfahrt International 7 - in fact, I've been long trying to dispel the myth that mine shells were designed as anti-bomber ammunition only.

If you have data on the Brandgranate for the MK 108, I could re-estimate the firepower for that gun. I have one data sheet suggesting 140 g chemical content and 500 m/s muzzle velocity, but unfortunately it does not give the projectile weight which would be necessary to establish the kinetic energy.

Regards,

Henning (HoHun)


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## Juha (Dec 26, 2008)

Hello Kurfürst
thanks for your comments, it seems that we agree in the subject matter even if we might sometimes disagree on methods of how to present some points.
Yes the question is very complex one and I also see Tony’s method more as a rule of thumb which correlates reality best in the middle ground as rules of thumb tended to do.

Hello HoHun
my point is that you need first to hit. And that explained why after arming Ki-44-II Otsu with two 40mm Ho-301s changed the wing armament of the next model (Ki-44-II Hei) to two .5 HMGs and even modified in field some Otsus to Hei armament configuration. Ho-301 simply had too low MV for an effective fighter armament even if its ROV of 450rpm was very high for 40mm weapon and it was an interesting try. Of course only hitting isn’t enough, the hit must also be effective.

Juha


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## HoHun (Dec 26, 2008)

Hi Juha,

>my point is that you need first to hit. 

In actual combat no doubt, but a formula for shell effectivess should be expected to work for tests on the proving ground too where the hit is assured by other means 

>Ho-301 simply had too low MV for an effective fighter armament even if its ROV of 450rpm was very high for 40mm weapon and it was an interesting try. 

I haven't seen any trajectory data, but the extremely low muzzle velocity suggests that the shells travelled on a rather steeply dropping curve.

To use such a gun successfully (which to make matters worse had only a small ammunition supply), it would probably have been necessary to close to the very short ranges of the Luftwaffe "Rammjäger". However, I don't think the Ki-44 was adequately armoured for that, as short-range defensive fire is rather deadly, especially if the fighter has not much of a speed margin over the bomber - which probably applies to the Ki-44 vs. B-29 situation.

Regards,

Henning (HoHun)


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## drgondog (Dec 26, 2008)

Kurfürst said:


> The most severe flaw of Tony's calculation of KE and CE total of the projectile is that it derieves CE from existing KE - but there's simply no corellation between the two! To use a simple example, how much greater is the explosion from a hand granade if I throw it away than if I hold it in my hand?
> 
> *K- while I tend to generally agree this point relative to the velocities we are discussing, Tony is absolutely correct as the velocities increase. The fundamental question is how does the energy of the system translate to force when the system is brought to rest?
> 
> ...



OTOH a BB sized solid particle hitting your head at 20000fps will vaporize your head.

Back to the debate at hand. The ammunition, delivered in sufficient quantity to the vital target area, in a small enough time delta for which the ammunition package is expended and the target remains in position, to ensure the destruction of the target - is 'adequate'

The target, if a B-17, requires a lot more 'killing' than an Me 109 or Mustang and therefore either the quantity of a lesser ammunition, or the quality of the greater ammunition is more of a factor. With lesser ammunition, the survivability of the attacking a/c on a B-17 should be less but I doubt this to be true against a P-51.

IMHO, the survivability of the Fw 190 and Me 109 in combat with a P-51 was not enhanced by virtue of superior firepower. 

One may debate forever the greater vulnerability of the 109 or 190 to an Mg 151/20 equipped Mustang over 4x 50.'s or 6x .50's. Intuitively? yes.


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## Juha (Dec 26, 2008)

Thanks Drgondog for the info on US fighter armour.
In Spitfire pilot's back armour was 4+7mm and head armour 6+6mm. at least in Mk XIV according to Alfred Price. Its purpose was to keep out MG 131 and MG 151/20 API from medium range, what ever it was, fired from inside 20 deg cone behind. So appr same than in Bf 109F/G but without the protection of fuel tank and the 22mm aluminium sheets armour. And I don't know the quality and type of armour.

Juha


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## Kurfürst (Dec 26, 2008)

I have some doubts about the XIV, I have never seen it described it as such, or having changed so radically from the Mk IX.

On the Mk IX the back plate was 4,5mm thick, the head plate was 6,2mm thick. There was no plate under the pilot, but there was a very small (88mm tall) plate behind his legs, at the level of the knee, again 6,2mm thick. There was no other pilot armor.

The upper fuel tank was protected by a plate in front of it, between the upper tank and the engine, 4,25mm thick; there was a inverted-U shaped cowling above the top tank, a deflector plate made out of aluminium of 3.5mm thickness, aimed to deflect rounds coming in from shallow angle.

This was supplemented by 38mm thick armor glass in the front of the canopy.

There was another iverted U shaped piece of armor in front of the horshoe shaped glycol tank between the engine and the propeller, of 6.2mm thickness.

There were 6.2 to 6.5mm thickness armor plates in front of the cannon ammunition boxes. 

The whole armor package weighted 71 kg. Information from a rather detailed German technical report from 1943.


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## Juha (Dec 26, 2008)

Hello Kurfürst
Yes I also think that Mk IXs and XIVs should have some kind protection at least late IX and all XIVs. According to Price's Spitfire book the back armour was 2 part system, 4 mm plate shaped like a L or a seat and a bit more backward a 7 mm thick straight plate. But of course it is possible that with heavier engine in nose it was possible to increase pilot's back armour. I have not seen any documents on the matter. If I would have time I would check from the Spitfire Bible but Shacklady's book is a bit haphazardy organized so finding something specific from it is somewhat difficult.

Juha

ADDITION: Out of curiosity made a quick look on Morgan's Shacklady's book. Didn't find drawings on armour layout but Spitfire Mk VIII had armour weight of 202lb, IX had 200 lb and XIV had 180 lb, so Germans seems to have missed something that weighted 20 kg, 200 lb is appr 90,7 kg.


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## slaterat (Dec 27, 2008)

Juha is correct. The extension of the nose some 18 inches in converting a mkV to a IX would necessitate ballast aft of the pilot hence the additional armour plate. The armour layout Kurfurst posted is that for a Spit V except there was also a 10 swg[3.5mm] aluminum deflector plate above and below the ammo boxes. It appears that the back plate was missed in the German report as well as the deflector plates on the ammo boxes.

Slaterat


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## Kurfürst (Dec 27, 2008)

slaterat said:


> The armour layout Kurfurst posted is that for a Spit V



No, it is for the Spit IX. The Spit V is also covered the report, but only differring marginally



> except there was also a 10 swg[3.5mm] aluminum deflector plate above and below the ammo boxes. It appears that the back plate was missed in the German report as well as the deflector plates on the ammo boxes.
> 
> Slaterat



The German report mentions all of these, as do my post.. The report contains everything that was there on the Spit IX.

The 200+lbs figure is extremely dubious, unless it counts items as 'armor' which are not that in the traditional sense, ie. weight of self sealing tanks. This is quite likely as these were quite heavy, the one in the Bf 109G weighting 121 lbs.

I have certainly not seen anything that would suggest a 'second' back plate on any Spitfire models.


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## Juha (Dec 27, 2008)

Hello Kurfürst
if you don't have seen anything that would suggest a 'second' back plate on any Spitfire models, why not take a look on page 101 in Price's Spitfire. A Complete Fighting History (1997)
And in Morgan and Shacklady p. 289 Modification 1193 for Mk VIII: Split armour for rear protection, it may well indicate to the armour layout that is in Price's book. BTW Morgan and Shacklady gives armour weight for Mk V as 73 lb. And for PR Mk XI no armour weight but same fuel capacity in fuselage tanks as in Mk IX which indicates that self-sealing isn't counted in armour weight.

It might well be that rear armour protection in Spitfire was reinforced in stages.

Juha


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## HoHun (Dec 27, 2008)

Hi Juha,

>Pilots saw 4*.5 HMG as adequate armament against Japanese a/c and saw also that after you had run out ammo your chances to help the defence of your flat-top or your charges was minimal. 

If you check the actual ammunition supply, the 4x 12.7 mm battery had 1720 rounds of ammunition while the 6x 12.7 mm battery had only 1440 rounds. What the pilot bemoaned was that the new aircraft had less ammunition, not that the extra guns fired off the same the number of rounds more quickly.

4x ,50 Browning M2 - 430 rpg, 33 s duration - 305 kg - 1,1 MW firepower - 37.5 MJ total supply
6x ,50 Browning M2 - 240 rpg, 18 s duration - 332 kg - 1,7 MW firepower - 31.4 MJ total supply

In fact, the F4F-4 example is great for showing what was wrong with the 12.7 mm Browning guns ... they were extremely heavy. 

Here is an alternative battery that would have done a much superior job:

2x Hispano II - 417 rpg, 42 s duration - 305 kg - 2,1 MW firepower - 88.5 MJ total supply

What would these cannon have done for the US navy?

- They would have increased firepower by a factor of almost 2 over the F4F-3 battery (at the same weight).
- They would have increased the total firing duration by a factor of 1.3 over the F4F-3 battery (at the same weight).
- They would have increased the total ammunition supply by a factor of 2.4 over the F4F-3 (at the same weight).
- It would have increased firepower by more than 20% over the six-gun battery of the F4F-4 (at lower weight).

So whatever way you look at it, the 12.7 mm Browning armament was inferior to contemporary cannon, and replacing it with a different type of gun would have had considerable performance and tactical benefits for the US forces.

>Pilots saw 4*.5 HMG as adequate armament against Japanese a/c and saw also that after you had run out ammo your chances to help the defence of your flat-top or your charges was minimal. And without flat-top... Simple as that.

Taking a second look at this statement, I find it to be a very good illustration for the danger of using the term "adequate" ... I know that you meant to describe the firepower of the four-gun battery which against unarmoured Japanese aircraft with unprotected fuel tanks, against which it obviously was lethal, but what you wrote - inadvertently, I guess - actually was "adequate armament".

As the weight and the available ammunition supply have to be judged along with firepower, and weight and ammunition supply were basically "much more than adequate" and "much less than adequate" respectively, the battery as a whole was "far from adequate". As the survival of an entire aircraft carrier depended on the quality of the guns of its fighters, your example is a great illustration that having obsolete and overweight aircraft guns is a problem even for the side that is winning the war.

Regards,

Henning (HoHun)


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## Clay_Allison (Dec 28, 2008)

HoHun said:


> Hi Juha,
> 
> >Pilots saw 4*.5 HMG as adequate armament against Japanese a/c and saw also that after you had run out ammo your chances to help the defence of your flat-top or your charges was minimal.
> 
> ...



The US Military had a rare bout of idiocy (rare at the time, they are more practiced now) where concerns the 20mm HS Cannon. Someone somewhere never realized that they were making a giant machine gun, not artillery and that tolerances would have to be finer to account for headspacing a cartridge at a high (comparatively) rate of fire. As a result, British guns, made with close tolerances, worked fantastically well. American guns were using greased ammunition to prevent them blowing themselves up when they were used, but mostly they were not used.


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## Kurfürst (Dec 28, 2008)

Juha said:


> Hello Kurfürst
> if you don't have seen anything that would suggest a 'second' back plate on any Spitfire models, why not take a look on page 101 in Price's Spitfire. A Complete Fighting History (1997)And in Morgan and Shacklady p. 289 Modification 1193 for Mk VIII: Split armour for rear protection, it may well indicate to the armour layout that is in Price's book.



Yes, it is possible, M+S does note that split armor in the rear, with a date for the modification of 20-12-43. Its a pity that there are no other detail about thickness and the extent of introduction to service aircraft, but I am sure it would be very useful, given that the existing 4.5mm plate was lacking in proctection offered. Unfortunately I don't have that particular Price book.



Juha said:


> BTW Morgan and Shacklady gives armour weight for Mk V as 73 lb. And for PR Mk XI no armour weight but same fuel capacity in fuselage tanks as in Mk IX which indicates that self-sealing isn't counted in armour weight.
> 
> It might well be that rear armour protection in Spitfire was reinforced in stages.
> 
> Juha



The German report as of 5 February 1943 indicates the armor weight on the Mk V being 60 kg, on Mk VI being 67.8 kg vs 70.8 kg on the Mk IX. The only difference striking to the eye is that the back plate is made up by 3 seperate plates while the IX covers the same area with a single plate, plus some minor difference in the form of the cannon armor plate and head plate.

It is quite certain they received upgrades, the Germans note that the glykol tank plate and the knee-plate were both found from autumn 1942 onwards, for example.


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## Glider (Dec 28, 2008)

Clay_Allison said:


> The US Military had a rare bout of idiocy (rare at the time, they are more practiced now) where concerns the 20mm HS Cannon. Someone somewhere never realized that they were making a giant machine gun, not artillery and that tolerances would have to be finer to account for headspacing a cartridge at a high (comparatively) rate of fire. As a result, British guns, made with close tolerances, worked fantastically well. American guns were using greased ammunition to prevent them blowing themselves up when they were used, but mostly they were not used.



I believe that this story which does appear every now and again is not true. Indeed in the various tests that took place the UK representatives were full of praise for the quality and fit of the american produced guns which were ahead of the British produced weapons.
They didn't work, because the USA refused to apply the changes to the original design that the British had made to make it work.


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## renrich (Dec 28, 2008)

Yep, practically a miracle that the US won the war and shot down all those Japanese and German AC armed with their superior cannon while the US was stuck with the outmoded, obsolete, overweight and merely adequate weapons. I wonder if any German or Japanese fighter plane had an edge in kills over an American fighter. I can think of a few that might not have done well. P39 in the Pacific and the P38 in the ETO. But wait, both of them were armed with cannon. Oh well, when one side has superior technology in AC and better trained and more aggressive pilots, they are bound to win.


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## KrazyKraut (Dec 28, 2008)

yawn


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## Clay_Allison (Dec 28, 2008)

renrich said:


> Yep, practically a miracle that the US won the war and shot down all those Japanese and German AC armed with their superior cannon while the US was stuck with the outmoded, obsolete, overweight and merely adequate weapons. I wonder if any German or Japanese fighter plane had an edge in kills over an American fighter. I can think of a few that might not have done well. P39 in the Pacific and the P38 in the ETO. But wait, both of them were armed with cannon. Oh well, when one side has superior technology in AC and better trained and more aggressive pilots, they are bound to win.


We were lucky in that my personal hero John Moses Browning designed the greatest and most enduring heavy machine gun of all time for us to chew up opposing airframes. We were equally lucky that we had no need to shoot down any heavy bombers like the Germans, British, and Japanese did. 

Cannon armament is nice but it only becomes really vital when you need to knock a B-17 out of the sky. Those big heavy airframes can take a ridiculous amount of MG fire.

With the US fighting mostly fighters, dive bombers, etc. we didn't really need a cannon armed interceptor. If we had, we probably would have put that T-9 37mm cannon from the P-39 in the P-38's nose.


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## HoHun (Dec 28, 2008)

Hi Clay,

>Cannon armament is nice but it only becomes really vital when you need to knock a B-17 out of the sky. 

That's a popular fallacy. Heavy machine guns were overweight and limited the capabilities of any aircraft that employed them. The extra weight was bad for fighter manouvrability and performance ... every US fighter that was shot down because it was not fast enough, couldn't climb well enough or didn't evade nimbly enough had been hampered by its own armament. And for those of them that would almost have escaped, the extra weight of the heavy machine guns alone was was killed them.

Even US bombers fell victim to the overweight of the US fighter guns ... whenever they were left in a tight spot because their fighter cover had to turn back for lack of fuel, they were exposed to enemy attack because the fighters did not carry as much as fuel they might have with more modern and weight-efficient guns.

Just have a look at this comparison:

6x ,50 Browning M2 - 400 rpg - 438 kg - 1,7 MW firepower
2x MG 151/20 - 250 rpg - 191 kg - 2,5 MW firepower

Going to a modern 1940s' armament option yields a weight advantage of 247 kg or about 545 lbs. These 545 lbs, had they been used for fuel, would have enabled the P-51D to extend its coverage by about 58 minutes at maximum continuous power at 25000 ft - almost one hour!

Being stuck with early 1930s' guns instead had many bad effects on tactics and operations, and undoubtly cost the US quite a number of fighters, bombers and a host of aircrew who were shot down because they were fighting with poor weaponry.

To assume that guns with objectively poor technical parameters did not make a difference to the worse just because the US forces "never had to shoot down heavy bombers" is rather naive - reality is more complex and less flattering than that.

Regards,

Henning (HoHun)


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## renrich (Dec 28, 2008)

The 50 BMG weighed substantially less than the US 20 mm and the ammunition less also. In a duel between fighters the odds of getting hits with four or six fifties are much better than with two 20 mm cannon. The British and American designers bureaus of aeronautics knew that. The British to the extent that they insisted on six fifties in the F4F4 probably because they realised that the British pilots would not have as much air to air gunnery training as the USN pilots.


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## drgondog (Dec 28, 2008)

HoHun said:


> Hi Clay,
> 
> >Cannon armament is nice but it only becomes really vital when you need to knock a B-17 out of the sky.
> 
> ...



LOL


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## Clay_Allison (Dec 28, 2008)

HoHun said:


> Hi Clay,
> 
> >Cannon armament is nice but it only becomes really vital when you need to knock a B-17 out of the sky.
> 
> ...


You know, I need to ask a friend of mine how much weight might have been saved if as much of the M2 as possible would have been made from aluminum (pretty common to use aluminum in guns these days). The US had plenty of aluminum and I can think of several large heavy parts that could be milled from aluminum.

Also I think using lighter weight explosive ammo would have made it more comparable to the German 13mm guns.


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## renrich (Dec 28, 2008)

Saw a news report the other day on a French corvette or something similar on patrol off the coast of Somalia looking for pirates and it showed one of it's gunners sighting on a ship they were checking. Lo and behold the idiots who designed the ship had put an M2 BMG on board, probably more than one and just think the best MBT in the world still has the old Ma Deuce as one of it's main weapons. Go figure!


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## Juha (Dec 28, 2008)

Hello Kurfürst
thanks for the details from German reports. M+S book is sometimes infuriating, giving wonderful details on some one-offs but not revealing some fundamentals as the exact details of different armour schemes. And lack of good index made searching info from it sometimes very haphazardly.

Hello HoHun
USN was interested in Hispano but didn’t want to heed British advices but wanted to solve problems themselves and so their 20mm cannon was at first very unreliable and when they got it more or less ready for service naval and IIRC also MC pilots preferred 6*.5 HMGs (F4U-1D) over 4*20mm (F4U-1C). Pilots seemed to think that 6*.5s was better in air combat but in strafing 4*20mm might have its merits.

Hello Renrich
one reason why RN demanded 6*.5s for F4F-4 was that one main enemy of their fighters was FW 200 Condor. 

Juha


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## Clay_Allison (Dec 28, 2008)

renrich said:


> Saw a news report the other day on a French corvette or something similar on patrol off the coast of Somalia looking for pirates and it showed one of it's gunners sighting on a ship they were checking. Lo and behold the idiots who designed the ship had put an M2 BMG on board, probably more than one and just think the best MBT in the world still has the old Ma Deuce as one of it's main weapons. Go figure!


The M2 .50 is one of the most common and available weapons on earth and while it wasn't perfect, you know what it does. It's just a solid, workmanlike gun.


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## HoHun (Dec 28, 2008)

Hi Clay,

>You know, I need to ask a friend of mine how much weight might have been saved if as much of the M2 as possible would have been made from aluminum (pretty common to use aluminum in guns these days). 

Hm, interesting thought. If you could share your friend's answer, that would be appreciated!

Historically, the route to improved firepower for the 12.7 mm Browning was to increase rate of fire. The Korean War era Browning M3 was a significant improvement in this respect.

However, if you look at the Mustang's battery, more than half of its total weight were ammunition, and a lighter or faster firing weapon can only bring a limited benefit.

6x ,50 Browning M2 - 400 rpg - 438 kg total, 264 kg ammunition

The total energy content of 20 mm rounds - MG 151/20 as well as Hispano - was roughly twice that of 12.7 mm rounds, so a change to a larger calibre with more capacity for explosives would have allowed cutting down the weight of ammunition for a certain effect on the target by one half.

As this is the larger share of the battery's total weight, it would seem more promising to go this route. As Tony Williams pointed out, the Japanese successfully up-scaled the 12.7 mm Browning M2 to 20 mm as the Ho-5 cannon, showing a feasible route the US might have taken too (even if just as a back-up option in case of the Hispano not working out as intended). 

The Ho-5 had some problems in service as well, but considering the small industrial base and limited metalurgical options the Japanese had, it's quite possible that development of an analogue cannon in the US would have posed no problems of this sort.

Regards,

Henning (HoHun)


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## Clay_Allison (Dec 28, 2008)

HoHun said:


> Hi Clay,
> 
> >You know, I need to ask a friend of mine how much weight might have been saved if as much of the M2 as possible would have been made from aluminum (pretty common to use aluminum in guns these days).
> 
> ...


Well the M2 was a scaled up 1919 so it makes sense you could scale it up again to 20mm. 

You also could have loaded the M2 with HE rounds as well. PETN weighs less than lead, and the 750 grains of lead is most of the weight of the ammunition.


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## renrich (Dec 28, 2008)

The first Condor shot down by a Wildcat was on Christmas Day, 1941, by a F4F3 with four guns and of couse the FM2 reverted to four guns. An interesting statement by Eric Brown in his comparison of the 109F versus the Wildcat. "The Wildcat had a heavier punch to deliver." He apparently believed that the wing mounted six fifties of the Wildcat were superior to the two rifle caliber Mgs and the 20 mm in the nose.


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## HoHun (Dec 28, 2008)

Hi Clay,

>>Lo and behold the idiots who designed the ship had put an M2 BMG on board, probably more than one and just think the best MBT in the world still has the old Ma Deuce as one of it's main weapons. 

>The M2 .50 is one of the most common and available weapons on earth and while it wasn't perfect, you know what it does. It's just a solid, workmanlike gun.

Note that the main defect of the 12.7 Browning M2, its heavy weight, has a quite different priority in an aviation context than in an armour or even naval context.

Six guns in a 5-ton-fighter that has to fly is not the same as one gun in a 50-ton-tank in a tank that doesn't have to fly, or any number of guns in a 3000-ton-ship.

Regards,

Henning (HoHun)


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## renrich (Dec 28, 2008)

No question that weight of a gun plays a great deal more of a role in an AC where every pound saved, especially in WW2 AC, is precious. The point made in my post on the BMG in the present is that if it were not extremely effective, it seems like it would have been supplanted or at least seriously modified. The ones I have seen in newscasts in Iraq and other areas seem to be identical to the one I used in 1960.


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## claidemore (Dec 28, 2008)

On the subject of .50 BMGs shooting down heavy bombers, I believe the Royal Navy Martlet I/Wildcats (with 4x.50s) shot down several FW200 Condors, a heavy 4 engine bomber. (as renrich pointed out)

Me323's also fell victim to P40's in North Africa, (I believe James 'Stocky' Edwards got 2 or 3 in one mission?) 

There were also a host of twin engine bombers that fell to .50 Brownings, both German and Japanese. 

Also, Anabuki Satoru shot down two P38s and two B24s with the twin 12.7mm guns on a Ki-43 (then rammed another B24 to become an "Ace in a Day") 

This belief that .50s were ineffective (against bombers) seems to stem from poor results in the popular IL2 series of flight sims rather than real life results.


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## HoHun (Dec 28, 2008)

Hi Claidemore,

>This belief that .50s were ineffective seems to stem from poor results in the popular IL2 series of flight sims rather than real life results.

What the real-life data right from Tony's site clearly shows is that the 12.7 mm Browning was inefficient, overweight and behind its times:

4x ,50 Browning M2 - 430 rpg, 33 s duration - 305 kg - 1,1 MW firepower - 37.5 MJ total supply
6x ,50 Browning M2 - 240 rpg, 18 s duration - 332 kg - 1,7 MW firepower - 31.4 MJ total supply
2x Hispano II - 417 rpg, 42 s duration - 305 kg - 2,1 MW firepower - 88.5 MJ total supply

Pick any Luftwaffe or Allied cannon, plug in the data, the result is always the same - the 12.7 mm Browning provides significantly less firepower for significantly more weight.

Regards,

Henning (HoHun)


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## HoHun (Dec 28, 2008)

Hi again,

>Last edited by claidemore : Today at 12:30 AM. Reason: (against bombers) 

Oh, that wasn't in your post when I clicked "reply".

>This belief that .50s were ineffective (against bombers) [...]

With the addition, I see your point - in fact, it's the exact mirror image of the common misconception that cannon are effectly only against bombers.

Regards,

Henning (HoHun)


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## KrazyKraut (Dec 28, 2008)

The Condor is a converted airliner and Me323 is a transport. Both don't fly in tight formations, both don't have a very impressive defensive capabilities. Attacking them is much easier and doesn't require dealing as much damage as possible in as little time as possible. At least not even nearly as much as a flight of B-17s does. Especially the Fw 200 was usually a complete loner.


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## Glider (Dec 28, 2008)

claidemore said:


> On the subject of .50 BMGs shooting down heavy bombers, I believe the Royal Navy Martlet I/Wildcats (with 4x.50s) shot down several FW200 Condors, a heavy 4 engine bomber. (as renrich pointed out).


The Condor was a converted passenger airliner with a weak spot in the rear of the fuselage. It wasn't built to stand the strains of battle as any normal bomber would be making it vulnerable.

.


> Me323's also fell victim to P40's in North Africa, (I believe James 'Stocky' Edwards got 2 or 3 in one mission?)
> 
> There were also a host of twin engine bombers that fell to .50 Browning, both German and Japanese. .


Absolutely true



> Also, Anabuki Satoru shot down two P38s and two B24s with the twin 12.7mm guns on a Ki-43 (then rammed another B24 to become an "Ace in a Day") .


This should be treated with more than the usual amount of caution. The combat happened on the 8th October 1943. The 495th Fighter Unit which was the only P38 equipped unit in India or Burma, didn't fly its first missions until 21st November. Secondly no B24's were lost in the combat zone on that day. Thirdly to expect one Ki43 to achieve this level of damage with 2 x 12.7mg's with their limited ammunition of 250 rpg is asking a bit much. There was some scepticism of his claims by some of the other Japanese Pilots

That said it is only fair to say that the Japanese did shoot a number of four engined bombers with the Ki43.


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## Juha (Dec 29, 2008)

Hello
Yes I know the FW 200 kills by Martlets/Wildcats but still the main adversarities of RN fighters were many time lone snoopers, so 6*.5s with fewer rpg made sense to it. After all, even if FC shot down hundreds of medium bombers in 1940 with 8*.303s it demanded 20mm Hispano armament for its future fighters.
BTW IIRC the first ever a/c destroyed by Martlet/Wildcat was a Ju 88 shot down by a RN Martlet pilot.

Gliber
my recollection is also that Anabuki's claims was badly inflated.

Juha


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## Timppa (Dec 29, 2008)

In choosing the aircraft armament, aspects such as war economy, production, contracts and even nationalism probably played big part.

Germans used rifle caliber guns (7.7mm) quite late, Bf109-G4 and Fw190A-6 still carried them. Spitfires, even the XIV, carried .303 guns to the last day. In America, 20mm cannon was only in limited production, perhaps also due to the fact that it was NIH (Not Invented Here), having French and British origin.
The Soviets seemed to be most flexible. Having the best rifle caliber MG (ShKAS and Ultra-ShKAS) and best heavy MG (UBT,UBK,UBS), they replaced them quickly after discovering that the cannons offered still more 'bang for the buck'.


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## HoHun (Dec 29, 2008)

Hi Juha,

>Yes I know the FW 200 kills by Martlets/Wildcats but still the main adversarities of RN fighters were many time lone snoopers, so 6*.5s with fewer rpg made sense to it. 

Just to make sure: If you had the choice of cannon, it never made sense to use the 12.7 mm Browning M2.

It always loaded your aircraft down more than any cannon battery, with all the inevitable negative consequences on performance and manoeuvrability this brings.

Here is the well-known comparison repeated for yet another aspect, equal ammunition capacity:

6x ,50 Browning M2 - 240 rpg, 18 s duration - 332 kg - 1,7 MW firepower - 31.4 MJ total supply
2x Hispano II - 150 rpg, 15 s duration - 174 kg - 2,1 MW firepower - 31.8 MJ total supply

It's amazing how often I can post facts and figures in this thread just to get the same old "but for XY, the fifties were good enough", with XY being everthing from "fighters", "Condors", "mounting it on a tank" or "mounting it on a ship". The only one that is missing is "using it as a boat's anchor", and that's almost the only honest assessment in a discussion of aircraft armament.

Regards,

Henning (HoHun)


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## claidemore (Dec 29, 2008)

Question:
The second series of Mustangs, the Mk1A's, were armed with 4 x 20mm Hispanos, and were in combat from 1941 until well after D-Day. 

Why did the subsequent models go back to the .50 Brownings? Since the RAF already had success with the Hispano, in both Spitfires and Mustangs, why didn't they put them in the MkII, MkIII etc? 

Anybody?

Claidemore

edit: interesting pic of Mk1as 
Mustang Ranch: 1942 | Shorpy Photo Archive


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## HoHun (Dec 29, 2008)

Hi Claidemore,

>Mustang Ranch: 1942 | Shorpy Photo Archive

Great picture, thanks! 

>Since the RAF already had success with the Hispano, in both Spitfires and Mustangs, why didn't they put them in the MkII, MkIII etc? 

I can only speculate, but during the war there was considerable drive towards standardization between the different services and between US and British users. As the USAAF was unlikely to adopt the Hispano cannon (since the US models had serious problems), the RAF probably had to accept standardization on 12.7 mm armament.

Regards,

Henning (HoHun)


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## renrich (Dec 29, 2008)

In my mind there is no question that two 20 mms in the wings, if they have ballistics similar to the the US 20 mms in Dean's book, are going to be more effective than four or six 50s in the wings. That is, they will be if the pilot can hit the target with them. If the ballistics are similar to the A6M's 20 mms then I believe the four or six fifties are more effective. The two issues are; can the target be hit equally as often with the two 20mms as with four or six fifties and do the 20mms have a flat enough trajectory and high enough velocity to allow them to be easy to hit with. The only other issue is ammo load. In the case of the A6M, the cannon had a low MV (and I suspect a poor ballistic coeffiecient) so they were a short ranged weapon and had a low ammo load. Those characteristics made the Wildcat a better armed AC. To boot, the early A6M had no armor and no ss tanks which made it not very resistant to 50 cal fire. It seems to me that, in a theoretical case, if one fighter has two guns and the other has four or six guns and the trajectories, velocities and rate of fire are the same, the fighter with four guns is twice as likely to get hits as the fighter with two guns and the fighter with six guns will get proportionately more hits than the other two. If the MGs have a higher rate of fire and higher velocity and flatter trajectory then that will increase their chances of getting hits and if the MGs have a longer firing time due to a greater ammo load then the chances of getting hits is increased more. The factor which then comes into play is the amount of damage each hit causes. In the case of the 303 British, if memory serves, their boffins postulated that it would take a two second burst with eight guns which would yield 397 hits(?) to bring down a bomber. In the case of the Rheinmetall 30 mm MK103 cannon the German boffins predicted that from 500 meters 40 hits from that weapon would bring down a four engined bomber 50 % of the time and 76 hits would bring it down 95% of the time. Between those two extremes would fall the performance of the 50 BMG and the 20 mms. Would each hit with a 20mm be twice as damaging or would that depend on where the hit occurred? My personal experience with the 50 BMG is that it has great destructive capabilities on ground targets such as trucks, half tracks and personnel carriers and my personal experience with airplanes(having owned a 172 and flown an L39) is that a similar sized WW2 fighter is not as robust as a two and one half ton truck. Having said that a 20 mm, if it hits and wherevever it hits, has got to do more damage than the 50 cal round. Hmmmm?


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## KrazyKraut (Dec 30, 2008)

Uh *40-76* hits by an MK-103 to bring down a bomber? How does that fit into the picture when at the same time 3-4 hits by the similar or slightly weaker MK-108 were considered enough? Or ~25 hits of the definetly weaker MG 151/20?


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## renrich (Dec 30, 2008)

Good point. I am quoting from a book entitled "The Great Book of WW2 Aircraft" and this info is in the section on the FW190. I suspect that the table is meant to show the probability of getting enough hits with the rounds expended to cause fatal damage. The table indicates that it is a 50% probability that 104 rounds from 1000 meters and 308 rounds from 1500 meters will bring down the bomber.


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## KrazyKraut (Dec 30, 2008)

Yes, I would assume you mean 40 to 76 _shots fired_ from an MK-103 to bring down a bomber with the probabilities quoted, that makes sense.


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## HoHun (Dec 30, 2008)

Hi Krazykraut,

>Uh *40-76* hits by an MK-103 to bring down a bomber? How does that fit into the picture when at the same time 3-4 hits by the similar or slightly weaker MK-108 were considered enough?

It's actually 76 rounds fired for a 95 % probability of kill, achieving 10 % hits at a medium combat range of 500 m.

http://www.ww2aircraft.net/forum/weapons-systems-tech/30mm-mine-shell-15789.html

>Or ~25 hits of the definetly weaker MG 151/20?

18 hits for 50 % probability of kill. For comparison, another report equates 20 hits of 20 mm MG 151/20 with 75 hits of 15 mm MG 151 ammunition. 

Since the MG 151/20 rounds were roughly twice as powerful as the 12.7 mm Browning M2 rounds, this would suggest something in the region of 150 hits or 1500 rounds fired for a 50 % kill chance on a heavy bomber.

This would equate to about 14 s of firing time for a battery of 8 Brownings, compared to about 5 s for a battery of 4 MG 151/20, making the bombers' return fire more than twice as effective against a Browning-armed fighter.

Regards,

Henning (HoHun)


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## claidemore (Dec 30, 2008)

My math isn't that great, but.....if the MG151/20 is twice as powerful as the .50 Browning, and it takes 20 hits from the 20mm to down a bomber, then wouldn't it take 40 hits from the .50? 

Looks to me like you might have doubled the 75 rds needed from the Mg151/15 to get 150 hits from the 8 brownings?

To get 40 hits from a 10% hit probability with 8x.50s you need just under 4 seconds of firing time.


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## HoHun (Dec 30, 2008)

Hi Claidemore,

>My math isn't that great, but.....if the MG151/20 is twice as powerful as the .50 Browning, and it takes 20 hits from the 20mm to down a bomber, then wouldn't it take 40 hits from the .50? 

Roger, that was a typo. It should have been:

"Since the MG 151 rounds were roughly twice as powerful as the 12.7 mm Browning M2 rounds, this would suggest something in the region of 150 hits or 1500 rounds fired for a 50 % kill chance on a heavy bomber."

So 75 hits required from an MG 151 with the original 15 mm calibre translate into roughly 150 hits required from a Browning M2 of 12.7 mm calibre.

The comparison of required firing times is correct as originally posted:

"This would equate to about 14 s of firing time for a battery of 8 Brownings, compared to about 5 s for a battery of 4 MG 151/20, making the bombers' return fire more than twice as effective against a Browning-armed fighter."

I chose the 4 MG 151/20 battery for comparison since despite the 15 mm cannon's good qualities (which the USAAF considered superior to the Browning M2), no Luftwaffe fighter ever used a battery of 4 15-mm-calibre MG 151 guns.

Regards,

Henning (HoHun)


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## HoHun (Dec 30, 2008)

Hi Claidemore,

>With only 10-5% accuracy, convergence issues really aren't an issue at all, in fact they will probably increase hit probability with the 'box' harmonization. The less accurate system (sic), will be more effective in combat. 

>[...]

>Basically a large 'box' harmonization of wing mounted guns would be capitalizing on the 90-95% expectation of missing the target, and turning that into a hit probability.

If that would be correct, we'd have seen the nose guns on fighters like the P-38 deliberately set up to diverge to reduce concentration of fire and increase effectiviness (as you suggest this would accomplish).

However, if you look at the bore sighting chart for the type, you'll see that the machine guns were only half a meter apart and set to fire parallel, and that the guns were carfully harmonized to converge in the vertical plane to give the highest concentration of fire possible.

There was nothing to stop the USAAF from increasing the size of the pattern of a nose-gun fighter, had they wanted to. However, they couldn't decrease the size of the pattern of a wing gun fighter for technical reasons.

That they didn't go for a large pattern when it was not enforced by technical reasons shows pretty clearly that they did not want the large patterns inevitable with wing gun fighters, but were stuck with them because there was no way to shrink them.

Regards,

Henning (HoHun)


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## HoHun (Jan 1, 2009)

Hi again,

"If you look at the bore sighting chart for the type, you'll see that the machine guns were only half a meter apart and set to fire parallel, and that the guns were carfully harmonized to converge in the vertical plane to give the highest concentration of fire possible."

In order to illustrate this point, I used the above boresighting chart for the P-38 to create the attached animated GIF, showing the sight picture for a straight six, no deflection "boresight" attack (placing the centre of the crosshair right on the centre of the target) against a P-47-sized fighter.

Ranges start with 100 m and increase in 100 m steps to 1000 m maximum.

Thin-line circles are 100 % hit circle, fat-line circles are 75 % hit circle.

The 20 mm cannon is indicated in red, the 12.7 mm machine guns in yellow and orange.

Basically this is the same kind of diagram as I have posted above for the P-47 and the Me 109K, just in a more compact presentation.

It was still more complicated to assemble because instead of one pattern per (half) battery, the new diagram has one pattern per gun. Additionally, I found that the P-38 boresighting chart gives surprisingly flat trajectories for some unknown reason, perhaps because because it illustrates the situation at 30000 ft or something. For comparison purposes, I established sea-level trajectory data from speed-over-range diagrams for the 12.7 mm and 20 mm armour piercing ammunition, using 12.7 mm trajectory data provided by Tony Williams (from "Machine Guns" by Max Popenke and Tony Williams) to verify that my calculation is sound. (Tony's data: Flight time to 1200 m 2.04 s, my calculation: 2.00 s, Tony's data: mid-range trajectory +510 cm, my calculation: +491 cm).

Anyway, I think the resulting diagram illustrates the excellent qualities of the P-38 as a gunnery platform quite well! 

Regards,

Henning (HoHun)


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## claidemore (Jan 1, 2009)

Hi Henning, 
Just wanted to point out that each set of 4 guns on a P47 are arranged in close proximity to each other (as in the P38 ). When they are not sighted for a 'box' harmonization, they will also give a good concentration of firepower, albeit with two 4-gun streams of projectiles with the attendant 'problems' of harmonization. At the harmonization range, there will be a double concentration of fire.

I agree that in a boresighting, on your six, no deflection type shot (as illustrated above), the P38 gun layout would be devastating. I just believe that in deflection shooting against a target that is moving on various planes, the box harmonized wing guns will have a greater chance of scoring a hit, and a hit of any kind is better than a complete miss with an overwhelming concentration of fire from nose mounted guns. 

Of course it wouldn't make sense to box harmonize nose mounted guns on a P38, it would negate a tangible advantage, concentrated firepower, and the choice between hit probability and concentrated firepower is clear for that fighter. 
On a wing mounted gun fighter the choice is not so clear. Concentrated firepower is less tangible, existing only at harmonization range, so a box harmonization does make sense, trading a less tangible concentration of firepower for hit probability. 
Since the vast majority of fighter pilots did not aim for specific parts of their target, ie O2 tanks/fuel tanks, cockpit, but rather at the whole plane, and were still missing 90% of the time, the 'shotgun' box harmonization seems like a pretty good choice. 
As was pointed out earlier, with the advent of computerized sights, nose guns are an obvious choice. High hit probability, combined with max damage from closely mounted parrallel guns. With reflector or ring and bead sights, and the attendant inaccuracy, I don't see wing guns as having any real disadvantages, only theoretical ones. 

Anyways, I still vote for the Beaufighter. It's got the best of both worlds, awesome firepower from centrally located 20mms, and six brownings spread out on the wings to spread destruction (sic) over a wide area.


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## Soren (Jan 2, 2009)

The Beaufighter lacks the destructive armament of other fighters though.

The Me-262 has the heaviest fighter armament featuring 4x 30mm cannons, while the Fw-190A-8/A-9 comes in as a close 2nd with 2x 13mm, 2x 20mm 2x 30mm cannons.


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## Clay_Allison (Jan 2, 2009)

HoHun said:


> Hi Juha,
> 
> >Yes I know the FW 200 kills by Martlets/Wildcats but still the main adversarities of RN fighters were many time lone snoopers, so 6*.5s with fewer rpg made sense to it.
> 
> ...



The fifties were what we used because the US cannons sucked. For some reason the War Department didn't want to take British advice so we screwed around all war without them. 

In retrospect, if it was me making the call in 1940, I'd neck up the .50 BMG case to 20mm and load HE rounds in a rebarrelled and lightened M2.

The result would have been much like the Japanese 20mm cannon in power. Less than many others, but light and very high damage/weight ratio. PETN weighs far less than lead.

Imagine a P-47 with 8 CANNON! That woud be incredible.


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## Glider (Jan 2, 2009)

Soren said:


> The Beaufighter lacks the destructive armament of other fighters though.
> 
> The Me-262 has the heaviest fighter armament featuring 4x 30mm cannons, while the Fw-190A-8/A-9 comes in as a close 2nd with 2x 13mm, 2x 20mm 2x 30mm cannons.



Just an idea, what about salvoing the rockets at a bomber box, that might well cause a problem or two and there can be little doubt what would happen if one hit.


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## Soren (Jan 2, 2009)

Glider,

While you're certainly right that a salvo of rockets is a deadly weapon against a bomber formation, the beaufighter didn't have available any air to air rockets. The Me-262 Fw-190 on the other hand both did, the R4M's, which were very effective in the role. (Esp. considering the high MV resulting in a close match in ballistics between the rockets Mk108 projectiles)

And as to what happens if a rocket hits home, you're right there as-well, it generally only took a single hit with a R4M to blow a bomber out of the sky, it was almost guaranteed.


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## Glider (Jan 2, 2009)

I was just having an idle moment and thought about the GA rockets. Might be worth a try, certainly heard of dafter ideas.


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## HoHun (Jan 2, 2009)

Hi Claidemore,

>Just wanted to point out that each set of 4 guns on a P47 are arranged in close proximity to each other (as in the P38 ). When they are not sighted for a 'box' harmonization, they will also give a good concentration of firepower, albeit with two 4-gun streams of projectiles with the attendant 'problems' of harmonization. At the harmonization range, there will be a double concentration of fire.

Hm, at harmonization range OK, but only there. If you look at my firepower comparison chart (which lists only the 12.7 mm machine guns for the P-38), you'll see that the P-47 when sighted for 250 m harmonization has an advantage only between 210 m and 280 m, despite having 8 guns instead of four! If you add the P-38's Hispano cannon, the two would be about equal even at the P-47's best range, with the P-38 being superior at all other ranges. 

(I'll have to re-calculate that diagram since it uses the trajectories from the boresighting charts for the types, which don't match the specific data I have for the ammunition types. I guess the P-47 diagram is only meant for illustrative purposes as there is no bullet drop data provided, but the P-38 diagram has actual bullet drop data, which leaves me a bit puzzled. The result of the re-calculation will be a decrease of hit power at long ranges due to the more steeply curved trajectories.)

>I just believe that in deflection shooting against a target that is moving on various planes, the box harmonized wing guns will have a greater chance of scoring a hit, and a hit of any kind is better than a complete miss with an overwhelming concentration of fire from nose mounted guns. 

Hm, actually the Luftwaffe war experience was that it was of little worth to merely damage an enemy aircraft as it would carry its pilot home and often could be repaired. That's why they came up with mine ammunition - it was designed to deal catastrophic damage the aircraft structure to make the target go down immediately.

With regard to probabilities, what counts is only the product of the probability of a hit and the hit's probability of a kill. This is often misunderstood - by moving the bullets' impact point away from the centre of the pattern, the probability of a hit for each bullet drops, while its destructiveness remains the same. The end result of a larger pattern is a decreased probability for a kill.

I guess one reason this is so often misunderstood is that the idea "a larger pattern will give at least some hits where a smaller pattern would have missed entirely" is correct. However, it's not complete in that it only covers the case where a larger pattern is beneficial, without taking into account that there is a larger number of cases where a smaller pattern is better.

These arguments also address the "shotgun" concept, which is basically the same and often comes up during air gunnery discussions. The Luftwaffe's gunnery instruction manual "Die Schießfibel" is quite clear on that: "Don't rely on weapon dispersion - it won't help you if your aim is wrong! You can see here clearly [2 sighting examples] how *accurately* you have to know and hold the lead if you don't want to score a complete miss. But if you think all you have to do is to adjust your machine guns to increase the pattern so that you're able to hit more reliably, this unfortunately is a mistake. You will end up like the wild huntsman in the picture on the right." [Cartoon, captioned: "What good are all the blunderbusses if every one of them just misses?")

>Of course it wouldn't make sense to box harmonize nose mounted guns on a P38, it would negate a tangible advantage, concentrated firepower, and the choice between hit probability and concentrated firepower is clear for that fighter. 

Hm, you have lost me there. Wouldn't the choice be the same for any type of fighter, provided that you actually have the choice (like with a nose-gun fighter)?

>On a wing mounted gun fighter the choice is not so clear. Concentrated firepower is less tangible, existing only at harmonization range, so a box harmonization does make sense, trading a less tangible concentration of firepower for hit probability. 

The boresighting chart for the P-47 does not envision box harmonization. I have prepared another animated GIF to show the P-47's pattern resulting from the standard boresighting procedure, choosing 300 m harmonization range so that there is one frame in the animation that shows perfect concentration. (The standard boresighting distances given are alternatively 229 m and 320 m, so that's close to the longer standard distance.)

>Anyways, I still vote for the Beaufighter. It's got the best of both worlds, awesome firepower from centrally located 20mms, and six brownings spread out on the wings to spread destruction (sic) over a wide area.

Hm, I think the Luftwaffe manual already pointed out that a large pattern doesn't help in air combat. However, the Beaufighter's wing guns might be highly useful for ground strafing. The total battery of the Beaufighter is not really that close to the top, though:

Me 262: 20,1 MW
Fw 190A-8/R2: 13 MW
Ta 152H: 7,6 MW
Fw 190A-8: 5,5 MW
Me 109K-4: 5,5 MW
Beaufighter Mk 21: 5,3 MW

(I'm assuming Hispano II cannon for the Beaufighter - it would be slightly better with Hispano V cannon instead.)

Regards,

Henning (HoHun)


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## HoHun (Jan 2, 2009)

Hi again,

>The Luftwaffe's gunnery instruction manual "Die Schießfibel" is quite clear on that: "Don't rely on weapon dispersion - it won't help you if your aim is wrong! You can see here clearly [2 sighting examples] how *accurately* you have to know and hold the lead if you don't want to score a complete miss. But if you think all you have to do is to adjust your machine guns to increase the pattern so that you're able to hit more reliably, this unfortunately is a mistake. You will end up like the wild huntsman in the picture on the right." [Cartoon, captioned: "What good are all the blunderbusses if every one of them just misses?"]

Here is the page with the sighting examples ...

Regards,

Henning (HoHun)


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## claidemore (Jan 2, 2009)

The Beaufighter might not have had air to air rockets, but it did have air to surface ones. Since we are not comparing just air to air ability, but total firepower, if you add up the 4 Hispanos, 6 Brownings and eight 60 lb rockets on the Beau, I'm not sure any other WWII fighter could match it. 

AFAIK the FW190A8/A9 could not carry both the 30mm guns and the 2 rockets, so it was an either or situation. 

Me262 shouldn't count, at least for this discussion, as the thread was originally for piston engined fighters, though nobody doubts the destructive capability of the 4x30mms.


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## Soren (Jan 2, 2009)

claidemore said:


> The Beaufighter might not have had air to air rockets, but it did have air to surface ones. Since we are not comparing just air to air ability, but total firepower, if you add up the 4 Hispanos, 6 Brownings and eight 60 lb rockets on the Beau, I'm not sure any other WWII fighter could match it.
> 
> AFAIK the FW190A8/A9 could not carry both the 30mm guns and the 2 rockets, so it was an either or situation.



You are incorrect claidemore, the Fw-190A-8/A-9 featured 2x 30mm Mk108 inside the outer wings instead of the 2x 20mm MG151/20's of the A-5/6 7, so there was plenty of room for rockets, which is also quite evident since there are plenty of pictures of A-8's carrying rockets.

And an armament of 2x 13mm, 2x 20mm 2x 30mm cannons easily beats 6x 12.7mm 4x 20mm any day. Plus the Fw-190 could use air to air rockets, the R4M's, as-well as the most powerful air to surface missiles available. 

So if the Me-262 isn't mentioned then it has to be the Fw-190 A-8/9.


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## HoHun (Jan 2, 2009)

Hi Claidemore,

>Since we are not comparing just air to air ability, but total firepower, if you add up the 4 Hispanos, 6 Brownings and eight 60 lb rockets on the Beau, I'm not sure any other WWII fighter could match it. 

Hm, we already have almost 300 posts in this thread dealing with air-to-air capabilities of barrel armament, so while I see your point, I'd still like to suggest opening a separate thread for air-to-ground armament and rockets ... I'm sure it will be just as popular is this one here 

Regards,

Henning (HoHun)


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## HoHun (Jan 2, 2009)

Hi Claidemore,

>Just wanted to point out that each set of 4 guns on a P47 are arranged in close proximity to each other (as in the P38 ). When they are not sighted for a 'box' harmonization, they will also give a good concentration of firepower, albeit with two 4-gun streams of projectiles with the attendant 'problems' of harmonization. 

For the sake of completeness, here the P-47 guns with "box" harmonization, with the pairs converging at 220 m, 253 m, 287 m and 320 m.

Regards,

Henning (HoHun)


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## slaterat (Jan 2, 2009)

Thats very talented Hohun. It does look very inefficient. The box harmonization I have read about refers to a small vertical/ horizontal spacing at the same set range for all of the guns. 

Slaterat


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## HoHun (Jan 2, 2009)

Hi Slaterat,

>It does look very inefficient. The box harmonization I have read about refers to a small vertical/ horizontal spacing at the same set range for all of the guns. 

Ah, I see. I agree that the purely convergence-range based "box" (if it can be called so) harmonization is quite inefficient - however, that's the setup which the graph on Emmanuel Gustin's site suggested.

Here is another animation for a vertical spacing of the guns, all set to 300 m convergence range. If one would use two different convergence ranges here, one would not have the "vertical stack" effect that is evident at 300 m here, but I thought I'd do one change at a time 

Regards,

Henning (HoHun)


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## Clay_Allison (Jan 2, 2009)

HoHun said:


> Hi Slaterat,
> 
> >It does look very inefficient. The box harmonization I have read about refers to a small vertical/ horizontal spacing at the same set range for all of the guns.
> 
> ...


The convergence on the P-47 was 500 yards, according to several pilots I've heard interviewed on the subject.


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## HoHun (Jan 2, 2009)

Hi Clay,

>The convergence on the P-47 was 500 yards, according to several pilots I've heard interviewed on the subject.

Hm, this seems a rather long range ... here is the boresighting chart for the type, suggesting 250 or 350 yards.

Of course, tactical experience could lead to deviation from this standard, but my impression was really that this deviation was more towards shorter than towards longer ranges.

Regards,

Henning (HoHun)


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## slaterat (Jan 2, 2009)

Thats great work Hohun. A picture is worth a thousand words.

Slaterat


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## HoHun (Jan 2, 2009)

Hi Slaterat,

>Thats great work Hohun. A picture is worth a thousand words.

Thanks  I would actually like to improve on that presentation, for example by showing the destructiveness of the fire by replacing the circles with transparent disks that are coloured more intensively where the killing power is greater. Problem is, I have no idea how to do that without increasing the manual labour necessary to render the animations by a factor of one-hundred or something 

(Currently, a big pattern looks "good" because you can see that it makes it easy to it. However, since the bullet density decreases with the square of the range within the same circle, this is not the whole story ...)

Regards,

Henning (HoHun)


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## HoHun (Jan 2, 2009)

Hi Juha,

>>Pilots saw 4*.5 HMG as adequate armament against Japanese a/c and saw also that after you had run out ammo your chances to help the defence of your flat-top or your charges was minimal. 

Amsel has just posted an interesting and highly relevant quote over here: http://www.ww2aircraft.net/forum/aviation/what-wrong-f4f-wildcat-16142.html

"Here is the text of a despatch from Admiral Nimitz to
Admiral King sent on 20 June 1942:

ALL AIR COMBAT REPORTS BATTLE OF MIDWAY EMPHASIZE EXTREME
AND APPARENTLY INCREASED SUPERIORITY PERFORMANCE OF 0 FIGHTERS
X ALTHOUGH THESE PLANES ARE MORE VULNERABLE THAN OURS THE 
PRIMARY SOURCE OF ANY COMBAT SUCCESSES TO DATE BY NAVY FIGHTING
PLANES HAS BEEN OWN EXPERT TACTICS OPPOSED TO FAULTY ENEMY
TACTICS X OVERALL RESULTS HAVE BEEN BAD AND WILL BE SERIOUS
AND POTENTIALLY DECISIVE WITH IMPROVEMENT THAT MUST BE EXPECTED
IN ENEMY TACTICS X 

CONSIDER ACTION ALL OF FOLLOWING LINES TO BE OF HIGHEST IMPORTANCE
X PROVIDE P-40F PLANES OR COMPARABLE TYPE FOR ALL MARINE FIGHTING
SQUADRONS ASSIGNED TO OUTLYING BASES X IF P-40F OR COMPARABLE TYPE
CAN BE MODIFIED FOR AIRCRAFT CARRIER OPERATIONS PROVIDE THESE
PLANES FOR CARRIER FIGHTING SQUADRONS X TAKE ANY POSSIBLE STEPS
TO LIGHTEN F4F4 AND INCREASE AMMUNITION CAPACITY EVEN AT COST OF
REDUCTION IN NUMBER OF GUNS X GIVE ABSOLUTE PRIORITY TO 
PRODUCTION AND DELIVERY NEW F4U FIGHTERS"

It re-enforces your point that the ammunition supply was seen as critically insufficient. There is no direct comparison made to the F4F-3, though of course the hint at a possible reduction of the number of guns is clear.

>If you check the actual ammunition supply, the 4x 12.7 mm battery had 1720 rounds of ammunition while the 6x 12.7 mm battery had only 1440 rounds. What the pilot bemoaned was that the new aircraft had less ammunition, not that the extra guns fired off the same the number of rounds more quickly.

As Ivan just pointed out in another thread, my weight for the 12.7 mm Browning ammunition was too low: http://www.ww2aircraft.net/forum/weapons-systems-tech/ww2-aircraft-gun-specifications-16005.html

So the comparison with the hypothetical Hispano armament would be yet more unfavourable for the Browning:

4x ,50 Browning M2 - 430 rpg, 33 s duration - 350 kg - 1,1 MW firepower - 37.5 MJ total supply
6x ,50 Browning M2 - 240 rpg, 18 s duration - 370 kg - 1,7 MW firepower -31.4 MJ total supply

Here the Hispano battery with equal firing duration, but superior firepower at lower weight:

2x Hispano II - 325 rpg, 33 s duration - 260 kg - 2,1 MW firepower - 69 MJ total supply

So it would be possible to have the original duration of fire of the original F4F-3 Browning armament at about twice the firepower while saving 90 kg of weight.

(Note that Nimitz' telegraph also strongly suggests that weight savings are necessary for the F4F.)

My error regarding the weight of 12.7 mm ammunition of course affects most comparisons I have made in this thread, but I thought this was the most interesting example, so I'd point it out here and leave the rest uncorrected for now.

(Thanks for bringing up the Wildcat example, I have to admit that I was fixated on the European Theatre before that 

Regards,

Henning (HoHun)


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## claidemore (Jan 2, 2009)

Soren said:


> You are incorrect claidemore, the Fw-190A-8/A-9 featured 2x 30mm Mk108 inside the outer wings instead of the 2x 20mm MG151/20's of the A-5/6 7, so there was plenty of room for rockets, which is also quite evident since there are plenty of pictures of A-8's carrying rockets.
> 
> And an armament of 2x 13mm, 2x 20mm 2x 30mm cannons easily beats 6x 12.7mm 4x 20mm any day. Plus the Fw-190 could use air to air rockets, the R4M's, as-well as the most powerful air to surface missiles available.
> 
> So if the Me-262 isn't mentioned then it has to be the Fw-190 A-8/9.



My mistake, you are correct that the R2 and R8's had the Mk108 'in' the wing.


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## fly boy (Jan 3, 2009)

i'd go with the .50cals just because it takes almost anything down in a few rounds , has good RPM and has good range.


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## Clay_Allison (Jan 3, 2009)

fly boy said:


> i'd go with the .50cals just because it takes almost anything down in a few rounds , has good RPM and has good range.


You're just trying to make Hohun angry.


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## HardwareFreak (Jan 3, 2009)

1. Excellent stable gun platform, no engine torque or rudder trim issues
2. Tightly grouped/focused battery of 5 guns
3. fairly high velocity ammo yielding minimal flight time increasing hit probability
4. A jammed gun/cannon doesn't cause yaw issues as with wing mounted guns
5. A one second or less burst of all 5 guns would down any Axis fighter almost regardless of hit placement due to the "buzz saw effect" of the armament.

Even in the hands of lesser experienced pilots, it was fairly easy to score hits with the P-38 due to the stable aircraft and the single tight projectile stream of the four .50s and the 20mm. Due to the concentrated fire a single burst did serious damage regardless of hit placement. No matter where the stream hit, serious structural damage was a result. Engine, wingroot, outer wing panel, cockpit, rear fuselage, tail--it didn't really matter. Bulkheads and spars were shredded and cut in half by the concentration of rounds in close proximity.

While the Whirlwind may have possessed many of the above attributes that made the P-38 such an excellent gun platform, only 112 Whirlwinds were built, and in service they continually had problems with the Peregrine engines. Whirlwinds saw such limited service it is impossible to judge their performance against the Luftwaffe. Therefore, I respectfully suggest that the Whirlwind is not worthy of consideration in this discussion.

If the F7F had the maneuverability of the P-38, and if it had actually seen combat, I may have considered it. However it came too late in the war to see real service.

I'm assuming the original poster was concerned with singe seat day fighters, so we can exclude the Black Widow. The Mosquito wasn't a fighter as much as an intruder, and didn't have near the maneuverability to tangle with the Bf 109 and FW 190, so it should be excluded.

I don't have hard numbers on any other aircraft, but IIRC there were a half dozen or more "aces in a day" flying the P-38. I don't know if this was common in other Allied or Axis aircraft, and obviously other factors come in to play than aircraft type. However, if it is the case that there were more "aces in a day" in P-38s, that says something about the firepower prowess of this aircraft vs others. That fact that both of America's top two WWII aces achieved all their kills whilst flying the P-38 is testimony to its firepower and fighter prowess.

I have read that there were experimental P-38 field installations of 8 .50s in the nose with the Hispano removed. If the additional 4 guns also had 500 rds each that would be a total of 4000 rds of .50 cal per sortie. This also would have yielded a cyclic battery rate of about 106 rounds/sec (assuming 800 rds/min per gun) firing in a spread of about 2 ft x 3 ft. The article I read didn't go into detail, but I'm guessing that, sadly, these 'gunship' P-38s were likely used mostly for ground attack in the Pacific theater. Oh, but what an awesome air-air gun battery this would have been. The firepower of a P-47 all packed tightly into the nose. If the weight of those extra 4 Brownings and the additional ammo didn't completely unbalance the aircraft, and it could still dogfight, my oh my what a predator this 8 gun P-38 would have been.


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## HoHun (Jan 3, 2009)

Hi Hardwarefreak,

>1. Excellent stable gun platform, no engine torque or rudder trim issues

Hm, the British Purchasing Commission noted that the P-38 required constant directional re-trimming after each power change because the two engines would never arrive at exactly the same power setting.

>2. Tightly grouped/focused battery of 5 guns

We agree on that. Have you seen the animated GIF above? 

>No matter where the stream hit, serious structural damage was a result. Engine, wingroot, outer wing panel, cockpit, rear fuselage, tail--it didn't really matter. 

Do you have a source on that?

`>This also would have yielded a cyclic battery rate of about 106 rounds/sec (assuming 800 rds/sec per gun) firing in a spread of about 2 ft x 3 ft.

Since you are new to this thread, please check out the paragraph on the "shotgun misunderstanding" above.

Regards,

Henning (HoHun)


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## Kurfürst (Jan 3, 2009)

HoHun,

Would it be too much to ask for a similiar animated GIF for the Bf 109G, with MG 151/20 or MK 108 central gun, and gunpods?


----------



## HoHun (Jan 3, 2009)

Hi Kurfürst,

>Would it be too much to ask for a similiar animated GIF for the Bf 109G, with MG 151/20 or MK 108 central gun, and gunpods?

Right now, I have collected the trajectory data and assembled the pieces, now it just remains to collect the screenshots and make the GIF 

(Exactly for the configuration you suggest, coincidentally!)

Regards,

Henning (HoHun)


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## HoHun (Jan 3, 2009)

Hi again,

>Would it be too much to ask for a similiar animated GIF for the Bf 109G, with MG 151/20 or MK 108 central gun, and gunpods?

Here it is! 

Regards,

Henning (HoHun)


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## Kurfürst (Jan 3, 2009)

Superb! BTW, you might find it interesting to check my site, I have just uploaded a rather theoretical study about turning calculations!


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## HardwareFreak (Jan 3, 2009)

HoHun said:


> Hi Hardwarefreak,
> 
> >1. Excellent stable gun platform, no engine torque or rudder trim issues
> 
> Hm, the British Purchasing Commission noted that the P-38 required constant directional re-trimming after each power change because the two engines would never arrive at exactly the same power setting.



Hello HoHUn,

The British Purchasing Commission received 'castrated Lightnings', with Allisons that rotated in the same direction, and without the GE turbochargers. This was their own doing as they didn't want the counter rotating engines that were required to make the P-38 work properly. They wanted the same engine in both nacelles to ease maintenance. This caused lateral torque problems, and is more to blame for their re-trimming issues than uneven throttle settings. If they'd have purchased the Lightning as it was designed, they'd not have had this issue. Or, at least, not to the extent that they did.



HoHun said:


> >2. Tightly grouped/focused battery of 5 guns
> 
> We agree on that. Have you seen the animated GIF above?



Absolutely. This is the main reason I vote for the P-38 as the answer to the question of this thread. If, for some odd reason, Lockheed had given it wing guns instead, I wouldn't even consider the P-38. And yes, those GIFs are kinda neat. I'm not sure how accurate they are, but they give an excellent graphical understanding of static trajectory. Unfortunately, most aircraft that were being fired upon were likely making evasive maneuvers.

Focused fire that does the maximum amount of damage in the smallest area is what kills vehicles the best, whether it's aircraft, tanks, trucks, etc. By disrupting the structural integrity of the vehicle, said vehicle will then, in essence, due to gravity or locomotion, destroy itself. If you destroy the integrity of a wing spar by punching enough holes in it, the wing is going to fold and come off the airplane, same with the tail spar(s). If you punch a hole though the turret of a tank with a high velocity AP round, the friction resulting from the high velocity round passing through the steel turret is going to create thousands of globs of molten steel. This often would ignite the ammunition magazine in the turret and thus blow the turret off the tank. Concentrated fire on the tracks of a tank or half track would often sever or damage a track link. If the vehicle then attempts to get underway, the track binds up and shreds itself. In essence, you make the vehicle destroy itself by introducing failure with concentrated localized damage. The P-38 was great at this because of its tightly grouped gun battery.



HoHun said:


> >No matter where the stream hit, serious structural damage was a result. Engine, wingroot, outer wing panel, cockpit, rear fuselage, tail--it didn't really matter.
> 
> Do you have a source on that?



That's not a direct quote from a print or web source. It's my own statement based on a combination of things, those being, mainly, episodes of Discovery Wings over the years with many pilot interviews, and videos of static tests of the P-38 gun battery against 1/2" steel plate and some airframes at various distances and angles, conducted by the USAAC. If a P-38 missed, it missed. But when it hit, it literally shredded the area it hit because of the tight grouping of the guns and the resulting large amount of ammo penetrating a small area on the target. I've also seen video of similar tests conducted on the "gun trucks" of the Vietnam war era. The gun spacing of the quad .50 turret in these trucks was a little wider than that of the P-38 gun battery, but the effect was very similar. Obviously the damage wasn't quite as extensive without the Hispano. Nonetheless, the gun truck quad .50 would also shred 1/2" steel plate out to 300 yards with few deflections even up to very steep off angle shots. At 70 degrees off angle, the number of ricochet rounds started increasing quite a bit. Keep in mind this is flat 1/2" steel plate. There are only 3 locations where this would be found on a fighter airframe (and it wouldn't be completely flat). These would be around the cockpit sides and floor, possibly around the fuel tank behind the cockpit in the rear fuselage, and under the engine cowling or bolted to the engine cradle. The .50 Browning, as with most .50 ammo of WWII from any nation, had zero problems penetrating the aluminum skin of any aircraft, and still had plenty of energy left to damage internal aluminum structural members, or to penetrate steel armor plate under the skin. The AP and standard 'ball' ammo of the 20mm was even more effective here. The reason the .50 Browning was more effective in the P-38 than many other US fighters mounting the same gun is the concentration of so many .50 projectiles in a confined area on the target. There's nothing magic about this, just simple physics. And, again, given the penetration power of the .50 BMG round, 10 to 20 of these rounds, combined with a couple of 20mm Hispano rounds into the same area, was often enough to destroy a wing spar or fuselage bulkhead causing structural failure of the airframe. The result was a wing or tail coming off the airplane due to the aircraft's speed and G load. If the cockpit area was hit, the armor plate was of little value and the .50s and 20mm would go right through it killing the pilot. Hits to the engine cowling would easily penetrate the steel armor plate and have sufficient kinetic energy remaining to damage the intake tubing, oil cooler lines and fuel lines. After the first few rounds weakened the armor plate, those following in flight would likely penetrate the engine block, igniting the fuel and oil in the engine manifold and oil passages. Add in a single hit from an AP round from the Hispno and the engine is toast in one hit, regardless of armor plate.



HoHun said:


> >This also would have yielded a cyclic battery rate of about 106 rounds/sec (assuming 800 rds/sec per gun) firing in a spread of about 2 ft x 3 ft.
> 
> Since you are new to this thread, please check out the paragraph on the "shotgun misunderstanding" above.



I've read the entire thread. I'm not sure what you're getting at here. I'm estimating that pattern as I don't know what the actual barrel spacing was on the 8 gun P-38. Obviously as the guns heat up you're going to get some fliers running around, and you'll have some variance from one gun to another, as with all aircraft. I'm not familiar with the sighting/alignment procedures the ground crews used to zero the P-38 guns. I can tell you that in the gun test videos I saw, the pattern on target was pretty darn tight.


----------



## HoHun (Jan 4, 2009)

Hi Hardwarefreak,

>The British Purchasing Commission received 'castrated Lightnings' [...]

Their negative comment was the result of a test of a standard Lightning as flown by the USAAF though, and thus applies to P-38s as flown by the USAAF as well. 

>And yes, those GIFs are kinda neat. I'm not sure how accurate they are, but they give an excellent graphical understanding of static trajectory.

Well, dig out some data and check the trajectories for yourself if you doubt. We can only learn from it ...

>Unfortunately, most aircraft that were being fired upon were likely making evasive maneuvers.

What's your source on that?

>The P-38 was great at this because of its tightly grouped gun battery.

The gun battery was "tightly grouped", but it was neither particular powerful nor did it have a particularly narrow cone of fire.

Here is the firepower comparison again:

Me 262: 20,1 MW
Fw 190A-8/R2: 13 MW
Ta 152H: 7,6 MW
Fw 190A-8: 5,5 MW
Me 109K-4: 5,5 MW
Beaufighter Mk 21: 5,3 MW
...
P-47D: 2,3 MW
P-38: 2,2 MW

These 2.2 MW at 300 m range impact over an area of more than 2.5 m^2, giving an average of less than 0.9 MW/m^2 firepower density.

At the same range, the nose guns of the Me 109K-4 impact in a pattern of about 1 m^2 area, giving an average firepower density of more than 5 MW/m^2.

>It's my own statement based on a combination of things, those being, mainly, episodes of Discovery Wings over the years with many pilot interviews [...]

I see.

>The .50 Browning, as with most .50 ammo of WWII from any nation, had zero problems penetrating the aluminum skin of any aircraft, and still had plenty of energy left to damage internal aluminum structural members, or to penetrate steel armor plate under the skin.

I guess you missed this information, posted earlier in this thread:



> A report on the Fw 190A-3 prepared by the Oxfordness Research station concludes that in an astern attack, neither 20 mm H.S. A.P., 20 mm H.E./T. (Fuze 253) nor 20 mm S.A.P./I. were able to penetrate the Fw 190's pilot armour when fired from a 10 degree sector after of the plane. The deflection of the projectiles by the aircraft skin and - when it came to the head armour - by the vertical tail was enough to reduce their penetration abilities to a fraction of the nominal value. It was not possible for any of the rounds (including 0.5" A.P.) to penetrate the engine cowling and damage the engine in this type of attack.
> 
> With regard to the fuel tanks, the effect you mention is specially stressed:
> 
> ...



>>This also would have yielded a cyclic battery rate of about 106 rounds/sec (assuming 800 rds/sec per gun) firing in a spread of about 2 ft x 3 ft.

>I've read the entire thread. I'm not sure what you're getting at here. 

It not the number of projectiles that makes a battery destructive, it is (unsurprisingly) the destructiveness of the projectiles that makes a battery destructive.

Regards,

Henning (HoHun)


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## HoHun (Jan 4, 2009)

Hi Kurfürst,

>Would it be too much to ask for a similiar animated GIF for the Bf 109G, with MG 151/20 or MK 108 central gun, and gunpods?

Here is another Messerschmitt for you, the Me 109F-1 with MG 151 in 15 mm and the 7.92 mm cowl guns. Some (very slight) inaccuracy in the cowl gun trajectories result from having to re-calculate the original trajectory data from the standard bullet to the "improved" bullet of higher muzzle velocity that was used in the MG 17.

Regards,

Henning (HoHun)


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## Clay_Allison (Jan 4, 2009)

> I have read that there were experimental P-38 field installations of 8 .50s in the nose with the Hispano removed. If the additional 4 guns also had 500 rds each that would be a total of 4000 rds of .50 cal per sortie. This also would have yielded a cyclic battery rate of about 106 rounds/sec (assuming 800 rds/sec per gun) firing in a spread of about 2 ft x 3 ft. The article I read didn't go into detail, but I'm guessing that, sadly, these 'gunship' P-38s were likely used mostly for ground attack in the Pacific theater. Oh, but what an awesome air-air gun battery this would have been. The firepower of a P-47 all packed tightly into the nose. If the weight of those extra 4 Brownings and the additional ammo didn't completely unbalance the aircraft, and it could still dogfight, my oh my what a predator this 8 gun P-38 would have been.



I've often thought that an 8-gun nose armament on the P-38 would be the ultimate allied air-to-air gun grouping for the Pacific Theater.


----------



## drgondog (Jan 4, 2009)

HoHun said:


> Hi Hardwarefreak,
> 
> >A report on the Fw 190A-3 prepared by the Oxfordness Research station concludes that in an astern attack, neither 20 mm H.S. A.P., 20 mm H.E./T. (Fuze 253) nor 20 mm S.A.P./I. were able to penetrate the Fw 190's pilot armour when fired from a 10 degree sector after of the plane. The deflection of the projectiles by the aircraft skin and - when it came to the head armour - by the vertical tail was enough to reduce their penetration abilities to a fraction of the nominal value. It was not possible for any of the rounds (including 0.5" A.P.) to penetrate the engine cowling and damage the engine in this type of attack.
> 
> ...



Makes one wonder if the same testing facility also concluded that .50 API would also be worthless for strafing German aircraft on the ground as well as worthless against locomotives, road and barge vehicles.

What a crock!


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## KrazyKraut (Jan 4, 2009)

Since armor protection layout seems to be arranged to protect from 6 o'clock and 12 o'clock on most WW2 fighters I'm not surprised it doesn't protect well against strafing aircraft.


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## drgondog (Jan 4, 2009)

KrazyKraut said:


> Since armor protection layout seems to be arranged to protect from 6 o'clock and 12 o'clock on most WW2 fighters I'm not surprised it doesn't protect well against strafing aircraft.



KK - when a battery of .50s perforate the steel hulls of barges, trucks, light armor and locomotive outer hull and boilers - it would be 'stretching' to conclude that they can't punch through aluminum skin, bulkheads, wing spars and engine blocks, or somehow is easily deflected by .032-.040 skin before smashing into a fuel tank. 

Huey skins are typically in that range and I GUARANTEE you that 7.62x39 will punch the crap out of them from any deflection angle. Please do not suggest to me that the 12.7 or .50 is somehow on the same par as that little bitch in air combat or ground to air..

How much combat film have you seen where a 109 or 190 simply lights up, then blows up from shallow deflection shots - granted not an extremely high percentage - but there is also the classic scene where the a/c simply rolls off in a shallow dive or roll and continues straight into the ground, a stitching into the engine with a resulting huge stream of coolant and/or steam from smashed engine block. 

It is just silly to postulate that 4 or six or 8 .50's were 'ineffective' when those weapons accounted for most of the Allied air and ground scores. 

That is my one and only point - not that .50 API is more destructive than the 20mm.


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## slaterat (Jan 4, 2009)

Dragon

Remember those RAF tests were at an angle of 10 degrees or less. At angles greater than that the ability of the skin to deflect rounds greatly decreases.

Also without having the actual testing procedures in front of us the results could be quite questionable. The RAF firing trials that I have read almost all 
have been based on single shots fired, not on bursts from a single or multiple gun battery. Of course this could give quite different results.

Slaterat


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## drgondog (Jan 4, 2009)

slaterat said:


> Dragon
> 
> Remember those RAF tests were at an angle of 10 degrees or less. At angles greater than that the ability of the skin to deflect rounds greatly decreases.
> 
> ...



SlateRat - I remember.

However, the ability of .032-.040 aluminum shear panels to cause 'deflections' and richochet's for .5 API is greatly overstated in this thread.


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## HardwareFreak (Jan 5, 2009)

I have a vivid memory of P-38 gun camera footage in which the pilot fires a very short burst into the nose of a Bf 109 from about 100-150 yards, 40 degrees or so off angle. The P-38 is behind the Bf 109 and to the right, firing into the right side of the nose. There are 10 or so small orange'ish impact flashes on the engine cowling directly behind the prop, the spread being no greater than 2 feet across (right to left) and maybe a foot in height. All the impact flashes were the same size, meaning he wasn't firing the cannon, just the Brownings. Almost instantly, the prop stops turning and fire and smoke start pouring out of the rear of the cowling right in front of the cockpit, as the Bf 109 slows rapidly and noses over out of control. I'm sure others have seen this same footage. It seems to be pretty popular footage for any TV program covering WWII air combat.

This one piece of footage demonstrates pretty dramatically the effectiveness of a 4 x .50 nose battery. One quick well aimed burst disabled a Benz DB601/5 behind thin armor plate, albeit at fairly close range. The effect at 300 yards would have been the same, although a bit more pilot skill would have been needed to pull off the longer range single burst kill of the engine.


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## HardwareFreak (Jan 5, 2009)

HoHun said:


> It not the number of projectiles that makes a battery destructive, it is (unsurprisingly) the destructiveness of the projectiles that makes a battery destructive.



Half of your posts I've read are fairly informative. Then you fire off statements like this, which are 180 degrees opposite of combat experience through two world wars and numerous conflicts since...

How can you state something like this with a straight face? Are you trolling?

You quoted "weight of fire" figures in the same post for pity sake. A critical component of weight of fire calculations *IS* the number of projectiles fired!

You contradicted yourself in the same post my friend.


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## HoHun (Jan 5, 2009)

Hi Hardwarefreak,

>>It not the number of projectiles that makes a battery destructive, it is (unsurprisingly) the destructiveness of the projectiles that makes a battery destructive.

>Half of your posts I've read are fairly informative. Then you fire off statements like this, which are 180 degrees opposite of combat experience through two world wars and numerous conflicts since...

Assuming to your favour that you are victim of a genuine misunderstanding, here is the full quote from the post I referred you to:

"With regard to probabilities, what counts is only the product of the probability of a hit and the hit's probability of a kill."

Since you assured me that you have read the entire thread, I trusted on you to realize that the "destructiveness of the projectiles" is proportional to the product of number of rounds that hit and one hit's probability of a kill.

>How can you state something like this with a straight face? Are you trolling?

1) You don't know anything about my face 

2) No.

3) And I don't consider a new account created exclusively for participating in a controversial thread a good basis to ask such question ...

>You quoted "weight of fire" figures in the same post for pity sake. 

Which "same post" are you referring to? This looks like another misunderstanding ...

Regards,

Henning (HoHun)


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## HardwareFreak (Jan 5, 2009)

HoHun said:


> Hi Hardwarefreak,
> 
> 3) And I don't consider a new account created exclusively for participating in a controversial thread a good basis to ask such question ...



That is a ginormous, and incorrect, assumption to make. This is my first and only account on this site, and until very recently (within the last week) I didn't know this site existed.



HoHun said:


> Which "same post" are you referring to? This looks like another misunderstanding ...



This is what I was referring to, from #307:



HoHun said:


> Here is the firepower comparison again:
> 
> Me 262: 20,1 MW
> Fw 190A-8/R2: 13 MW
> ...





HoHun said:


> It not the number of projectiles that makes a battery destructive, it is (unsurprisingly) the destructiveness of the projectiles that makes a battery destructive.



The point I was making is that those very firepower figures you pasted include within them the combined rate of fire of the aircraft's gun batteries, as well as many others qualities, including explosive shell power, penetration factor, etc.

It's not my intention to beat you up and make this a 10 page argument. All I'm saying is that you contradicted yourself. Obviously unintentionally, but nonetheless, you did. You have corrected yourself in your post immediately above when you state that "number of rounds that hit" is a factor. This obviously isn't an absolute as a "lucky" shot to a critical location, say a pilot's head, doesn't rely upon multiple rounds for a kill. This is obviously a very rare exception. The majority of aerial kills were the result of multiple hits on the target, and in the absence of those multiple hits, would not have been kills.


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## HoHun (Jan 5, 2009)

Hi Hardwarefreak,

>>And I don't consider a new account created exclusively for participating in a controversial thread a good basis to ask such question ...

>That is a ginormous, and incorrect, assumption to make. 

5 posts in total, all in this thread, account created well after this discussion started, claiming to have read all of the thread ... that's the data I have on you.

And you accused me of trolling in your post #4 ... how about an apology now that I have corrected your misunderstanding?

I might be guilty of using a less than perfect formulation, but I can hardly think of a more offensive way of asking for clarification than the one you chose.

>This is what I was referring to, from #307:

Your misunderstanding again - Watt is power, not weight.

>All I'm saying is that you contradicted yourself.

Your personal misunderstanding contradicted what seems to be an otherwise OK understanding of my posts ... you should have realized that after I posted my clarification.

Kind regards,

Henning (HoHun)


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## Clay_Allison (Jan 5, 2009)

HoHun said:


> Hi Hardwarefreak,
> 
> >>And I don't consider a new account created exclusively for participating in a controversial thread a good basis to ask such question ...
> 
> ...


I like your style, really. But I have to say that I know far more about guns than I do about aircraft, and I know that with a multitude of impacts each successive one is more damaging than the first, especially when hitting in rapid succession and creating a "stacking" effect of energy transfer. How many hits you can make is very important to how destructive any weapon is.


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## HoHun (Jan 6, 2009)

Hi Clay,

>But I have to say that I know far more about guns than I do about aircraft, and I know that with a multitude of impacts each successive one is more damaging than the first, especially when hitting in rapid succession and creating a "stacking" effect of energy transfer. How many hits you can make is very important to how destructive any weapon is.

Hm, would you still agree that it is the product of the number of hits and the probability of kill of each hit that counts?

I'm not sure if the stacking effect is really applicable in air combat ... how quickly would have two 12.7 mm hits follow each other (and with which precision) to achieve this? A P-47 with guns converging at 300 m averages about 17 bullet strikes per second per square meter in the 75 % radius of its pattern, so the likelihood of two hits on exactly the same spot in a very shrot period is not that great.

In fact, my impression is that the advantage of high-powered explosive shells is that they concentrate a lot of damage in a localized area, similar to the stacking effect you suggest except that it only requires one hit to induce a lot of energy, which due to their ability to critically damage aircraft structure makes them more destructive than a greater number of hits of the same energy which spread the energy of a larger area.

I'm not aware of any wartime reports on this - the Luftwaffe from their gun camera films of bomber shootdowns concluded that the total amount of explosives counted, regardless of calibre. Though they preferred 30 mm cannon over 20 mm cannon, that was more due to economy of scale making the 30 mm cannon a more weight-efficient weapon ... the greate localization of damage with larger shells did not play a role for them.

Regards,

Henning (HoHun)


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## Clay_Allison (Jan 6, 2009)

> I'm not sure if the stacking effect is really applicable in air combat ... how quickly would have two 12.7 mm hits follow each other (and with which precision) to achieve this? A P-47 with guns converging at 300 m averages about 17 bullet strikes per second per square meter in the 75 % radius of its pattern, so the likelihood of two hits on exactly the same spot in a very shrot period is not that great.



It doesn't have to be the same spot, it just has to be on the same contiguous piece of metal. When a bullet strikes it, a shock wave travels through it, "ringing" it. If another bullet hits before the shock wave is expended through vibration it forces the metal to absorb more energy and dramatically decreases its' ability to distribute (and thus absorb) the force of the impact, increasing the chance of penetration or failure of structual integrity.

I agree that a 20mm give you more bang for your buck, so to speak. But successive impacts do affect armor.


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## HoHun (Jan 6, 2009)

HI Clay,

>When a bullet strikes it, a shock wave travels through it, "ringing" it. 

Hm, how long does it usually take for the shock wave to dissipate?

Regards,

Henning (HoHun)


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## Clay_Allison (Jan 6, 2009)

HoHun said:


> HI Clay,
> 
> >When a bullet strikes it, a shock wave travels through it, "ringing" it.
> 
> ...


It would depend on the mass of the armor and angle of impact, a second would be my guess for a pilot armor plate, hit it twice in the same burst and the second round would have much more chance of going through.

I've seen .50s tear armored land vehicles to shreds both from the ground and strafing including armored locomotives with literally tons of armor. I heard a WWII Thunderbolt ace say when he caught an enemy plane in his convergence range he could disintegrate it, and I've seen the gun cams to prove it. Like it or not, the P-47 had a positive kill ratio with the Fw 190.

I think you are RIGHT about 20mm vs. 12.7mm, but you make it out like the .50 could not possibly damage a plane and I've seen it done. You are overselling your case a little.


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## HoHun (Jan 6, 2009)

Hii Clay,

>I've seen .50s tear armored land vehicles to shreds both from the ground and strafing including armored locomotives with literally tons of armor. 

On the other hand, if you look into US American WW2 aircraft manuals, they specifically indicate arcs of protection against 12.7 mm fire that is provided by the standard aircraft armour plates of the day. This was the same military that considered the 12.7 mm machine gun a good air-to-air weapon.

You might well be right that successive hits had a better penetration ability, but the various WW2 tests quoted in Tony's book "Flying Guns" also show that some hits had almost no pentrative ability due to rounds being disturbed after cutting through the non-armoured light alloy skin of the aircraft, so I don't see much reason to revise my assessment of the 12.7 mm machine gun effectiveness.

>I heard a WWII Thunderbolt ace say when he caught an enemy plane in his convergence range he could disintegrate it, and I've seen the gun cams to prove it. Like it or not, the P-47 had a positive kill ratio with the Fw 190.

Oh, kill ratio is the least of my concerns. The war is already over, you know 

With regard to destructiveness: Note that pretty early in this thread I quoted the USAAF pilot Riemensnider with his comment that a correctly ranged burst from the P-51's (only six) guns was "highly destructive", so I don't doubt that the P-47's battery could be even more destructive under the same circumstances.

>I think you are RIGHT about 20mm vs. 12.7mm, but you make it out like the .50 could not possibly damage a plane and I've seen it done. 

Actually, I don't think I have ever called the 12.7 mm guns ineffective. I might have called them obsolete, overweight, behind the state-of-the-art or, tongue-in-cheek, even boat's anchors, but I think you would be happy with the appraisal Riemensnider gave them if you'd browse back to quote I mentioned. I believe his statement is quite rational and well-considered, and I've been using his quote countless times over the years.

What gunnery discussions on the internet are often lacking is in fact the rational approach ... much of what you'll read when browsing back is really romanticism as the result of anecdote-based history perception. The WW2 reports quoted in this thread often paint a different picture ... and they were designed to win a war, not to make nice stories for the next generations.

Regards,

Henning (HoHun)


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## Clay_Allison (Jan 6, 2009)

HoHun said:


> Hii Clay,
> 
> >I've seen .50s tear armored land vehicles to shreds both from the ground and strafing including armored locomotives with literally tons of armor.
> 
> ...


Something that might have bridged the gap in terms of firepower on American versus other aircraft is the emphasis on gunnery in American fighter training. I've heard a lot of references to the gunnery school in the US during the war, and not to the Germans or Japanese having a similar program.


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## Soren (Jan 7, 2009)

Clay, the Luftwaffe had gunnery schools just like the USAAF did, no difference.


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## drgondog (Jan 7, 2009)

Soren said:


> Clay, the Luftwaffe had gunnery schools just like the USAAF did, no difference.



Soren - I believe this to be true, as in "how could they not?" but confess I have never seen photos of LW Gunnery schools or heard them mentioned in any of the biographies or conversations.

Where were they and what was the syllabus?


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## lesofprimus (Jan 7, 2009)

This is news to me, I would love to hear about the Luftwaffe Gunnery Schools....

Ive read countless accounts of guys doing Staffel gunnery practice, but not an actual "School"...


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## Clay_Allison (Jan 8, 2009)

lesofprimus said:


> This is news to me, I would love to hear about the Luftwaffe Gunnery Schools....
> 
> Ive read countless accounts of guys doing Staffel gunnery practice, but not an actual "School"...


that was my impression.


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## jrb53 (Jan 11, 2009)

"Blond Knight of Germany" -about some Hartmann guy  

"On 24 August 1942, while attending the advanced gunnery school at Gleiwitz, he flew down to Zerbst and demonstrated some of Lieutenant Hohagan's aerobatics over the airfield."

Jack


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## DerAdlerIstGelandet (Jan 11, 2009)

jrb53 said:


> "Blond Knight of Germany" -about some Hartmann guy
> 
> k



Whats wrong with the Hartmann "guy"?


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## delcyros (Jan 11, 2009)

In Vaarlose / Denmark was a gunnery school for the fighter arm, too. It´s an less well known unit, perhaps best known by the inofficial use of three Fw-187 A0, resulting in occassional fighter combats over southern Norway and Denmark.


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## jrb53 (Jan 11, 2009)

*DerAdler*- there is nothing "wrong" with Erich Hartmann. I consider him one of the best pilots of WW2. I also consider him a fine person and great example of German courage, intelligence, and perserverance. His caring attitude toward fellow pilots displayed on the Eastern Front were so outstanding that he became a natural leader in the post-war German air force. 

Note the "  " symbol. I was being light-hearted because several posts mention reading pilot biographies. To me, "Blond Knight of Germany" is a Classic (along with Thunderbolt, Samurai, Wing Leader, etc.) and I was very surprised that these forum members are not familiar with this biography.

I apologize for deviating from the original topic of this thread, I was merely referencing that the Luftwaffe did have gunnery schools.

Jack


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## DerAdlerIstGelandet (Jan 11, 2009)

jrb53 said:


> *DerAdler*- there is nothing "wrong" with Erich Hartmann. I consider him one of the best pilots of WW2. I also consider him a fine person and great example of German courage, intelligence, and perserverance. His caring attitude toward fellow pilots displayed on the Eastern Front were so outstanding that he became a natural leader in the post-war German air force.
> 
> Note the "  " symbol. I was being light-hearted because several posts mention reading pilot biographies. To me, "Blond Knight of Germany" is a Classic (along with Thunderbolt, Samurai, Wing Leader, etc.) and I was very surprised that these forum members are not familiar with this biography.
> 
> ...



No worries. I just did not understand thanks. Thanks for clarifying.


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## HoHun (Jan 11, 2009)

Hi everyone,

To get back on topic, here is another diagram for the Me 109F-0 with MG FF/M engine cannon and MG 17 cowl guns.

Regards,

Henning (HoHun)


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## HoHun (Jan 11, 2009)

Hi again,

And here is te Me 109E-4 with MG FF/M wing cannon and MG 17 cowl guns (based on the Me 109C-3 manual, the first cannon-armed variant that was overtaken by events and never built).

Regards,

Henning (HoHun)


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## renrich (Jan 11, 2009)

As the originator of this thread, ME262 should not be compared as it is not piston powered. The P61 should be considered because it was a pursuit(fighter). It had 4-50s and 4-20mms with a throw weight of 17.96 pounds /second.
The damage that the 50 BMG will do is incontrovertible no matter how much theory is thrown out. All of us have seen combat film of P47s blowing up locomotives with 50 BMGs. To intimate that it might not be effective against AC is ludicrous. The British thought enough of the 50 BMG to use two of them in the E wing of the Spit MarkIX, perhaps the best mark of the Spitfire. The Japanese went to 12.7s in the Zero and the Germans did in some of their fighters also. 
I believe the US used the 50 BMGs in all their fighters because it was very effective against the enemy AC they faced, it was reliable, available in large quantities, the armorers could service it easily and it's widespread use in all the US inventory of AC made ammunition supply easy.
The bottom line is that the war was won with 50 BMGs doing the job both in the ETO and the Pacific. There possibly could have been better weapon choices for all US fighters as far as ballistic effectiveness was concerned but taking all in consideration the 50 BMG was the best choice for the US.


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## Soren (Jan 12, 2009)

All German fighter pilots had to go through gunnery school (FliegerSchützenSchule), Erich Hartmann did it as-well.

There were several of these schools, including the Værløse Luftwaffe FliegerSchützenSchule in Denmark.

You can read about some of them here:
Various schools


And then here about the FliegerSchützenSchule for bomber gunners, later renamed to BordSchützenSchulen in 1942 (as written), the designation FSS still used for the fighter pilots. And up until very late in the war it was a 5 month process: 
Kampfflieger: Bomber Crewman of the ... - Google Bogsøgning


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## lesofprimus (Jan 12, 2009)

Thanks for the info, its something totally new to me....


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## drgondog (Jan 12, 2009)

Soren said:


> All German fighter pilots had to go through gunnery school (FliegerSchützenSchule), Erich Hartmann did it as-well.
> 
> There were several of these schools, including the Værløse Luftwaffe FliegerSchützenSchule in Denmark.
> 
> ...



Good info - wonder if LW had the equivalent 'Clobber College' that 8th AF imbedded in each of the operational Groups to transition from Goxhill, Atcham, Cheddington and Halesworth Transition schools?

The 355th had on base at Steeple Morden two 2 seat mod Mustangs, an AT-6 for transition training plus an A-35 and A-20 for Tow Target ships . to teach the newly arrived pilots a more refined set of operational skills after Goxhill. The A-35 and A-20 ships were rotated out to 2AD to serve all of the 65th Fighter wing gunnery training.

What was the operational focus and support doctrine for LW pre-combat/post advanced flight school Gunnery and tactics training?


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