# Aircraft armament....



## Lucky13 (Nov 18, 2008)

Which was the best aircraft fitted gun/cannon of WWII? And, why did the RAF stick with .303, what was their reasoning behind, why not go for bigger like .50's?


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## Doubl3Ac3 (Nov 18, 2008)

if i had to guess it was for more ammo. the .303 could do a fair amout of damage with a short burst. In the same matter the .50 could do the same in just 1 shot. the difference is size and weight, the .303 is alot lighter and smaller and is alot easier to lead a target with compared to the .50 which is alot heavier and take alot more skill to lead a target


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## DerAdlerIstGelandet (Nov 18, 2008)

I think best weapon depends on what you are gunning for. 

As a bomber killer I would want a larger caliber weapon such as the ones manufactured in Germany: *MG FF 20mm Cannon* armed with high explosive *Minengeschoss*, or the *MG 151/20 20mm Cannon* armed with high explosive *Minengeschoss*, or even the *MK 108 30mm Cannon* armed with high explosive *Minengeschoss*.

If I was doing just regular air to air combat with other fighters or light aircraft the US *.50 Cal* was just fine for the job and that is what I would want.


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## drgondog (Nov 18, 2008)

DerAdlerIstGelandet said:


> I think best weapon depends on what you are gunning for.
> 
> As a bomber killer I would want a larger caliber weapon such as the ones manufactured in Germany: *MG FF 20mm Cannon* armed with high explosive *Minengeschoss*, or the *MG 151/20 20mm Cannon* armed with high explosive *Minengeschoss*, or even the *MK 108 30mm Cannon* armed with high explosive *Minengeschoss*.
> 
> If I was doing just regular air to air combat with other fighters or light aircraft the US *.50 Cal* was just fine for the job and that is what I would want.



Chris - I'm pretty much with you on all points. I would like to have seen 51s with four of the MG151/15 or 20mm as the standard configuration. Suspect there would have been more German a/c shot down but difficult to prove.

As to a 303 being easier to 'lead'?? - I would doubt it. I don't understand the logic on that comment.

The 50 had 5x more mass and superior Ballistic coefficient so would experience less velocity loss and drop in trajectory for meaningful ranges and far more punch per round. If you are referring to a hand controlled waist gun 50, maybe the recoil would be more difficult to manage for a leading/tracking deflection shot but that would be pretty subjective.


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## HoHun (Nov 18, 2008)

Hi Lucky,

>Which was the best aircraft fitted gun/cannon of WWII? 

The MK 108.

>And, why did the RAF stick with .303, what was their reasoning behind, why not go for bigger like .50's?

They did not expect to fight armoured aircraft, and they overestimated the penetration power bullets have after passing through the aluminium skin of an aircraft.

Here is a firepower comparison, based on total muzzle energy (kinetical plus chemical, based on the equivalent of the shell's chemical content if it were TNT). The list is sorted by firepower per weight (including guns, ammunition and belting/drums), which is the most important limiting parameter for an aircraft gun battery. The ammunition supply is chosen to give the same total muzzle energy total for all rounds. The reference weapon is the US 12.7 mm Browning M2:

1x MK 108 - 87 rpg - 111 kg - 221% firepower - firepower per weight: 900%
1x MK 103 - 75 rpg - 210 kg - 180% firepower - firepower per weight: 387%
2x MG 151/20 (MX) - 187 rpg - 164 kg - 124% firepower - firepower per weight: 342%
2x MG 151/20 - 207 rpg - 172 kg - 112% firepower - firepower per weight: 294%
2x Hispano V - 212 rpg - 188 kg - 109% firepower - firepower per weight: 262%
2x Hispano II - 206 rpg - 201 kg - 94% firepower - firepower per weight: 211%
3x MG-FF - 149 rpg - 235 kg - 103% firepower - firepower per weight: 198%
5x MG 151 - 239 rpg - 428 kg - 97% firepower - firepower per weight: 102%
10x MG 131 - 311 rpg - 413 kg - 93% firepower - firepower per weight: 102%
8x ,50 Browning M2 - 250 rpg - 452 kg - 100% firepower - firepower per weight: 100%
25x Browning ,303 - 399 rpg - 549 kg - 96% firepower - firepower per weight: 79%
25x MG 17 - 406 rpg - 596 kg - 95% firepower - firepower per weight: 72%

The list is a bit "uneven" because I tried to avoid "fractional" guns in the batteries  Except for the rifle calibre machine gun batteries which would have been a nightmare to fit into a typical WW2 fighter, all of these batteries could have been realistically used in most fighter types of the era.

In my opinion, the question is not so much one of the best gun, but one of the best battery. I'd mix different weapon types, for example one nose-mounted MK 108 and two wing-root mounted MG 151/20 with MX shells in the mix. (The data is based on typical belting patterns for all guns.)

1x MK 108 - 87 rpg - 111 kg - 221% firepower - firepower per weight: 900%
2x MG 151/20 (MX) - 187 rpg - 164 kg - 124% firepower - firepower per weight: 342%

Total battery: 298 kg - 345% firepower - 523% firepower per weight

The advantage of the mixed battery is that you have extremely high firepower at short ranges and under good conditions (with a non-manoeuvering target) thanks to the MK 108 and still decent firepower at longer ranges due to the higher muzzle velocity of the lower fire-power MG 151/20.

Regards,

Henning (HoHun)


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## renrich (Nov 18, 2008)

The later model Spits did go with the 50 cals mixed with cannon. I also don't understand the comment about easier to lead with 30 cal. The MV of the two rounds was about the same and the BC of the fifty was so superior that the downrange velocity of the fifty was much faster and flatter shooting. I think the only reason the Brits used the 303 as long as they did was because that is how they started out and perhaps could not change in a hurry because of the redesign necessary and perhaps could not get the guns easily for the 50 cal. They also had a propensity for wanting a lot of guns and screwed up the F4F4 by insisting on a six gun battery instead of the four in the F4F3.


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## pbfoot (Nov 18, 2008)

here is the reasoning for the 8 303's in Brit aircraft
" after the Schneider races of 31 and the resulting speed record tacticians concluded that at such speeds a fighter would only have one chance to destroy its prey - the first attack-and that chance would last precisely 2 seconds . Ballistics experts showed a battery of 8 machine guns firing 1000 rounds a minute each would be needed to destroy a bomber in 2 seconds .Senior officers brought up on 2 syncronized forward firing Vickers guns raised their eyebrows . WC AT Willliams and SQn Ldr later Air Marshall Sir RS Sorley however took up the cause of the 8 gun fighter and when Williams its ardent and original champion died in 1934 it was Sorley more then anyone else who was responsable for its adoption by the RAF. 
It was the confluence of this tacticle need the work already being carried out by Camm and Mitchell the arrival of the Merlin and the browning machine gun that bore fruit in Specification F.5/34 (revised later to F36/34) The American Browning was a "first class weapon " with a rate of fire of 1260 rpm .A perfect example of intimate collaboration between airman and designer was Sorleys's test showing that in order to achieve a lethal density of bullets the Brownings would have to use their maximum rate of fire . This meant that they would have to be clear of the propellor arc which in turn meant the the wings would require speciak strength and rigidity - which Camm and Mitchell promptly undertook to provide
From AHB/II/116/17 ,p82 ,fn2


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## HoHun (Nov 18, 2008)

Hi Pbfoot,

>and I aint typing any more unless requested

Interesting stuff, keep it coming please! 

Regards,

Henning (HoHun)


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## lesofprimus (Nov 18, 2008)

There was also the point that the Brits had an obscene amount of .303 ammo laying around, so that if they changed out the caliber of gun, all that ,303 ammo would go where???


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## pbfoot (Nov 18, 2008)

HoHun said:


> Hi Pbfoot,
> 
> >and I aint typing any more unless requested
> 
> ...


I added the remainder to the original post


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## kool kitty89 (Nov 18, 2008)

*les*, that's true, but it should be noted that there were shortages of the most effective .303 rounds, particularly the "De Wilde" incendiary types (B.Mk.VI, and later B.Mk.VII) early in the war. A large amount of ball ammo was aparantly used due to shortages of more effective types.
THE BATTLE OF BRITAIN


> The 'De Wilde' bullets were first issued in June 1940 and tested operationally in the air battles over Dunkirk. Their improved effectiveness, coupled with the fact that the flash on impact indicated that the shooting was on target, was much appreciated by the fighter pilots. It was at first in short supply, and the initial RAF fighter loading was three guns loaded with ball, two with AP, two with Mk IV incendiary tracer and one with Mk VI incendiary. Another source for the Battle of Britain armament gives four guns with ball, two with AP and two with incendiaries (presumably Mk VI) with four of the last 25 rounds being tracer (presumably Mk IV incendiary/tracer) to tell the pilot he was running out of ammunition. It is not clear why ball was used at all; presumably there was a shortage of the more effective loadings. (By 1942 the standard loading for fixed .303s was half loaded with AP and half with incendiary.)




And the .303 would still have plenty of use on the ground.


There's an interesting new article on Tony Williams' site on British aircraft armament: http://www.ww2aircraft.net/forum/weapons-systems-tech/raf-guns-ammunition-15659.html#post420628


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## HoHun (Nov 19, 2008)

Hi Pbfoot,

>I added the remainder to the original post

Thanks!  

>This meant that they would have to be clear of the propellor arc which in turn meant the the wings would require speciak strength and rigidity - which Camm and Mitchell promptly undertook to provide

I'm a bit sceptical about the "strength" bit ... at least the Spitfire was designed for just two machine guns per wing, and the installation of the additional two not originally foreseen by the designer was actually very awkward and ballistically inefficient.

>From AHB/II/116/17 ,p82 ,fn2

Hm, I have to admit that I'm unable to decode this ... some RAF internal history document perhaps?

Regards,

Henning (HoHun)


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## kool kitty89 (Nov 19, 2008)

It should be noted that the British did have a competent heavy machine gun in the .5" Untitled Document which was somewhat lighter than the Browning though it fired the less powerful 12.7x81 Vickers round. (this also would have meant lower recoil forces on the wings of the smaller RAF fighters)

The reasoning behind staying with the .303 was from:
RAFHS 08


> Vickers was in the process of developing a scaled-up version of their .303" MG, chambered for a new .5" (12.7 mm) cartridge. This was produced in three versions for army, naval and aircraft use and was tested by the RAF in the mid-1920s against the new .50" Browning heavy machine gun, which was bigger and more powerful. The conclusion was that neither offered sufficient advantages to replace .303" MGs, since the slightly bigger hole they could punch wasn't adequate compensation for their greater size and weight and their lower rates of fire. The Swiss Oerlikon 20 mm cannon, developed from the German Becker of the Great War, was also tested in the late 1920s and early 30s and proved more promising since its explosive shells could do a lot more damage than just punching bigger holes, but it was big, heavy and slow-firing.



Of course this would be ignoring the larger incendiary content of the .50 round even if you exclude the armor variable from the equation. (it would also do greater damage to structural components) 
They instead made the choice, as many know, to go straight to 20 mm cannon if a harder hitting weapon was necessary, but the Hispano, while an excellent weapon was not ideal for all the situations a HMG woud be useful. (particularly in smaller fighters and for defensive armaments) So they got stuck with mixed armaments (retaining 4x .303 guns + 2x 20mm on Most Spitfires) and almost exclusively the .303's in defensive (flexible/turret) instalations.


Incedentally both the Italian 12.7 mm aircraft guns and the IJA Ho-103 (a derivative of the Browning) used the 12.7x81SR ammunition, the semi-rimmed export version of the .5" Vickers round.


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## renrich (Nov 19, 2008)

Really interesting stuff PB, KK, etc. Many thanks. I read an article in "Air and Space" a while back that ties into Pb's post which said that the two second burst would amount to 270 hits(or something like that) which was what it would take to bring down a bomber. I would like to hear from those in the know how the recoil from the various weapons load would impact the fighter. I have a reference that mentions that in a F8F if the cannons on one side had a stoppage it really introduced a yaw component.


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## Glider (Nov 19, 2008)

I think its worth remembering that when the decision was taken to arm the RAF fighters with 8 x LMGs, this was considered by all forces to be a pretty heavy armament.
The 109 of the same period had 3-4 x LMG, The Italians had 2 x HMG, The Japanese 2 x LMG, the USA often had 1 x HMG 1 x LMG, The French had 1 x 20mm and 2 x LMG.
Against this, 8 x LMG wasn't to be sniffed at.

Its also worth remembering that before the war that the UK knew that the 303 wasn't a long term solution and that the 20mm Hispano was the way to go. The problem was of course, that the 20mm took longer than expected to be made reliable.

As for the HMG, I dont disagree that it was the best weapon for bomber defence and was sufficient for attacking other fighters and smaller bombers. However, if you had to go up against a 4 engined bomber then I believe it would have been lacking.


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## renrich (Nov 19, 2008)

The US Navy in the Pacific felt that the 50 cal was quite effective aginst surface ships up to the size of and including DDs. There were instances of patrol craft and small coasters being disabled by AC armed with 50 cals.


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## pbfoot (Nov 19, 2008)

renrich said:


> . I would like to hear from those in the know how the recoil from the various weapons load would impact the fighter. I have a reference that mentions that in a F8F if the cannons on one side had a stoppage it really introduced a yaw component.


Not in the know but heres a good little tale from JP Coyne DFC RCAF 263 Sqn Whirlwind pilot 
"....always game I did a few flights on their Hurricane MkIV then had a go at their MKIX Spit again without the benefit of a handbook or even good advice. I took the Spit down to the gunnery range in the Channel and fired away , I was startled when the Spit went into a great skid . Immediately I stopped firing and pulled out from my dive realizing I had a cannon stoppage"


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## Airframes (Nov 19, 2008)

Very interesting stuff! The answers from PB et al all fall in the category of 'correct'. There was, of course, another reason why the .303 inch round remained in R.A.F. service throughout WW2. Basically, as one person has mentioned, it had to do with stocks, and also manufacture and supply. This calibre of ammunition had been in (general) service since before WW1, and was manufactured not only in the U.K., but also in the (then) 'Colonies', particularly, and in very large quantities, in India. (it still is in the latter!) It should be remembered that, in the early stages of WW2, Britain was not in a position to cope with the changes required, on a massive scale, in order to change a 'standard' ammunition, used in a broad spectrum of weapons. These changes would not only effect the tooling-up of the factories, but also the logistics chain, spares and repairs, training, armourers tooling etc etc.
Also, apart from the accepted point that Britain had foresaw a (then) powerful weapon in an eight gun fighter (remember, the aircraft is just the means of getting the guns to the target, and the guns are only the delivery system for the real weapon, the bullet/shell), and adding this fact to the above, the British 'Powers that be' were slow, if not reluctant, to effect change. (To a point, they still are.) Even immediately after WW2, when the value of heavier armament, air and ground, was already known and accepted, it still took years to change. Then, plans were already mooted to change calibres of some weapons, in particular, infantry weapons and, in this case, the 'Powers' were already looking at a probable smaller calibre round, but with a high, or higher, velocity and power to weight ratio. Eventually, the British forces changed to what became the NATO standard, 7.62mm (.30 Cal) but that didn't happen until 1958! The current British infantry weapon (being generous with such a title!) the L85, more commonly called the SA80 (translated, heap of ****) stemmed from a 1947 design, the EM2, which had been originally designed around a short 7.62 round, but was also tested, and proven, with various smaller calibres. This weapon could have been in service long before the L1A1 SLR (licence built, semi-auto FN FAL), but, for want of a better term, was 'held back', for various 'political' reasons, and didn't actually go into full service until 1985! I had been involved in some of the field trials of earlier production-prototypes of this weapon as early as 1976! 
So, apart from the logistics situation, and the massive stocks of .303 ammo, there was also the 'Establishment' to contend with. How we (Britain) ever achieved anything, considering the amount of b****y red tape (that still abounds) constricting things during WW2 will never cease to amaze me!
So, apologies for such a long winded response, and some (neccessary) digressions, but hopefully you will have understood what I mean! Basically, large stocks, dedicated calibre weapons, difficulty of change-over, logistics, and 1920's thinking in a World that was already, technologically, advancing faster in the five years of war than it had in the previous 100!


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## Glider (Nov 19, 2008)

Airframes said:


> Very interesting stuff! The answers from PB et al all fall in the category of 'correct'. There was, of course, another reason why the .303 inch round remained in R.A.F. service throughout WW2. Basically, as one person has mentioned, it had to do with stocks, and also manufacture and supply. This calibre of ammunition had been in (general) service since before WW1, and was manufactured not only in the U.K., but also in the (then) 'Colonies', particularly, and in very large quantities, in India. (it still is in the latter!) It should be remembered that, in the early stages of WW2, Britain was not in a position to cope with the changes required, on a massive scale, in order to change a 'standard' ammunition, used in a broad spectrum of weapons. These changes would not only effect the tooling-up of the factories, but also the logistics chain, spares and repairs, training, armourers tooling etc etc.


This argument doesn't hold up when you remember that we were doing all these tasks to bring the 20mm into service. 


> Also, apart from the accepted point that Britain had foresaw a (then) powerful weapon in an eight gun fighter (remember, the aircraft is just the means of getting the guns to the target, and the guns are only the delivery system for the real weapon, the bullet/shell), and adding this fact to the above, the British 'Powers that be' were slow, if not reluctant, to effect change. (To a point, they still are.)


If we are discussing the aircraft weapons then this statement I would question. Despite having the 20mm Hispano V arguably the best 20mm of the war, the British didn't hesitate to develop the 30mm Aden when the US were still using the 0.50 M3.


> Even immediately after WW2, when the value of heavier armament, air and ground, was already known and accepted, it still took years to change. Then, plans were already mooted to change calibres of some weapons, in particular, infantry weapons and, in this case, the 'Powers' were already looking at a probable smaller calibre round, but with a high, or higher, velocity and power to weight ratio. Eventually, the British forces changed to what became the NATO standard, 7.62mm (.30 Cal) but that didn't happen until 1958! The current British infantry weapon (being generous with such a title!) the L85, more commonly called the SA80 (translated, heap of ****) stemmed from a 1947 design, the EM2, which had been originally designed around a short 7.62 round, but was also tested, and proven, with various smaller calibres.
> This weapon could have been in service long before the L1A1 SLR (licence built, semi-auto FN FAL), but, for want of a better term, was 'held back', for various 'political' reasons, and didn't actually go into full service until 1985! I had been involved in some of the field trials of earlier production-prototypes of this weapon as early as 1976!


Again I must question some of these points. The ground breaking EM2 was designed for a brand new .280 round which we wanted to use in Nato in 1948, indeed the EM" was chosen as the new Army rifle in 1951. This wasn't allowed because the USA wanted to stick with the 7.62.
So the British were keen to change the round, as were the Belgian FN Company who were impressed with it and started to develop their own weapons around it. 
As for the SA80 there is no doubt it was a disaster when introduced but has developed into a reliable weapon.


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## renrich (Nov 19, 2008)

I do remember the British favoring the 280 and somewhere I seem to remember them wanting to go to the 270(277) which I feel would have been a laudable choice. This may have been before WW2.


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## Glider (Nov 19, 2008)

renrich said:


> The US Navy in the Pacific felt that the 50 cal was quite effective aginst surface ships up to the size of and including DDs. There were instances of patrol craft and small coasters being disabled by AC armed with 50 cals.



I would certainly believe that wooden patrol boats and small coasters would be at risk but would be suprised if anything bigger would be at risk.

The USN were quite keen to introduce the 20mm, all F6-F5 Hellcats were capable of being equipped with 2 x 20 and 4 x 0.50. 
Postwar I believe the USN were quick to introduce the 20mm whilst the USAAF stuck with the 0.50.


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## renrich (Nov 19, 2008)

Actually, The plating of a DD was subject to being penetrated by the 50 cal especially with AP rounds and at fairly close ranges. Many of the gun mounts were open and the bridge structure was not armored to any extent. The older DDs, the sub chasers and minesweepers as well as small freighters were especially vulnerable. The reason the USN and belatedly the USAF went to the 20 mm was that a single hit from a 20 mm explosive shell was more likely to put an AC out of commission than a single 50 cal. The 50 cal relied on kinetic energy and penetration for it's disabling qualities. Statistically a given number of 20mm rounds would have a much better chance of fatally damaging an AC than would the same number of 50 cals. There is quite a lot of combat film showing Japanese shipping being strafed by AC with 50 cals. Of course one cannot see how much damage is being done. The 50 cal AP round would penetrate .75 inches of armor plate at 547 yards. I don't believe that the upper works or decks of any WW2 DDs had armor plate. The 50 cal AP round would easily penetrate an AC engine block or the side armor of a German half track or light armored car according to Wiki.


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## Glider (Nov 19, 2008)

I don't disagree with what you say but knocking out some of the gunners and exposed crew would only rarely put a ship of any size out of action.
RAF Mossie and Beaufighters tasked with attacking escorts were well armed with cannons, machine guns and most importantly rockets. Even these were not expected to put the escorts out of action, just keep them quiet while the specialist torpedo/bomber aircraft went for the high value targets.

The rockets were the key weapon, most escorts lost to air attack (normally armed trawlers) were the result of attack by these weapons.

I am not aware of any vessel of any size being lost to HMG fire


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## kool kitty89 (Nov 19, 2008)

The .50 also had chemical energy in the API/I rounds. (the pure incendiary rounds being a simplified derivative of the British B.Mk.VI "De Wilde" bullet)
Which is important to remember with fire bing the big a/c killer. One major problem with the .50 in Korea was that with the less flamable Jet fuel (compared to gasoline) and the high altitudes often encountered, the API bullets often failed to ignite.



Glider said:


> I think its worth remembering that when the decision was taken to arm the RAF fighters with 8 x LMGs, this was considered by all forces to be a pretty heavy armament.
> The 109 of the same period had 3-4 x LMG, The Italians had 2 x HMG, The Japanese 2 x LMG, the USA often had 1 x HMG 1 x LMG, The French had 1 x 20mm and 2 x LMG.
> Against this, 8 x LMG wasn't to be sniffed at.
> 
> ...



It would certainly have been better than the .303's though. And the .5 Vickers had been around since the 20's and, though passed up by the RAF, was in use on the ground and at sea in its water cooled form.

The Spitfire should have been able to carry at least 4, and proabably 6. (there would be only a slight gain in empty weight with 4x ~10 lbs, but ~60 lbs with 6x)


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## Glider (Nov 19, 2008)

I will need time to dig it out but I am pretty sure that the vickers .5 was considered and took part in some trials in the mid 30s with other weapons but was rejected due to its weight and lack of performance.


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## kool kitty89 (Nov 19, 2008)

Yes, the RAF rejected it (along with the US .50 Browning) as I mentioned in post # 13:



> Vickers was in the process of developing a scaled-up version of their .303" MG, chambered for a new .5" (12.7 mm) cartridge. This was produced in three versions for army, naval and aircraft use and was tested by the RAF in the mid-1920s against the new .50" Browning heavy machine gun, which was bigger and more powerful. *The conclusion was that neither offered sufficient advantages to replace .303" MGs, since the slightly bigger hole they could punch wasn't adequate compensation for their greater size and weight and their lower rates of fire.* The Swiss Oerlikon 20 mm cannon, developed from the German Becker of the Great War, was also tested in the late 1920s and early 30s and proved more promising since its explosive shells could do a lot more damage than just punching bigger holes, but it was big, heavy and slow-firing.



Tests of the 1921 version of the Browning and the contemporary Vickers .5" were found in favor of the Vickers. (though the M2 version was significatly improved)

In any case it would seem they overestimated the destructive power of the .303 compared to the .50 and overlooked the longer range and incendiary carrying ability. (weight for weight the incendiary capacity was about the same, but the larger rounds were significantly more likely to do damage) 

It also seems to have been ignored that, despite significantly greater weight and lower rate of fire, it eventually becomes impractical to mount huge batteries of LMG in place of fewer HMG's of similar destructive power. They did manage to get up to 12x .303's in the Hurricane IIB (as well as the originally specified armament for the Typhoon and several others) but this takes a lot of space an would certainly not work in the Spitfire, while 6x .50 Vickers would fit much better, weigh a bit more, and have longer range. (and be much more powerful than the 8x .303 carried by the Spitfire, while still being able to fit, while more .303's woudn't)

While the 20 mm was obviously another step up the .50 would have been sort of an ensurance policy in case of developmental problems with the 20 mm, not to mention problems with mounting the much larger weapons.


In the '20s and early '30s the LMG's would generaly seem advantageous, but by the mid '30s it should have been clear that the progression of larger and stronger aircraft structures would leave the .303's lacking. (even without armor plate) At which time it was far from too late to adopt the .5" gun in addition to later adopting a 20mm weapon.



Even stranger, Rolls Royce was developing a Heavy aircraft machine gun (with emphesis on flexible/turret mountings) in the early 1940's, starting with a recoil operated version firing .50 BMG rounds, then gas operated gun in 1941, then a version using the .55 Boys ammunition. Work was abandoned in 1942. But why go through that trouble when you've got a decent HMG in the Vickers or just producing a modified version of the .50 Browning?


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## slaterat (Nov 20, 2008)

Somewhere in one of my books I recall something being said that RAF testing showed that for the equivalent weight of guns .303s would do more damage to an aluminum airframe than .50 s. Its not too hard to imagine how one could draw this conclusion as 2 x 303s could put 2400 rpm into a target compared to only 650-700 for a single .50. The main limitation of the .303 or all rcmgs , as I see it, is that they are too easily defeated by light armour plate and self sealing tanks.

Kitty 89 wrote



> In the '20s and early '30s the LMG's would generally seem advantageous, but by the mid '30s it should have been clear that the progression of larger and stronger aircraft structures would leave the .303's lacking. (even without armor plate) At which time it was far from too late to adopt the .5" gun in addition to later adopting a 20mm weapon



Keep in mind that the Air Ministry issued a spec for a 4 cannon armed fighter in 1936. In response Hawker proposed a 4 cannon Hurricane which was declined. Eventually the Hurri IIC did surface 5 years later.

Slaterat


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## kool kitty89 (Nov 20, 2008)

Yes and there were 4x cannon Spitfire V's, though not that common and the configuration was less than ideal. (too much recoil for the flexible wings of the early spitfires iirc)

As I said, the 20 mm was still in development at that time though, attempt of wing mounting the drum-fed Hispano went nowhere and the Mk.II wasn't available until after the BoB. The .5 Vickers could easily have been put into service as a suplemental gun, subsequently phasing out the .303 for aircraft.

Weight for weight, the .303 Browning is a bit more powerful, but, gun for gun the .50 was just over 2x as powerful and the Spitfire could have carried more than 1/2 the number of .50 guns than it could .303. (though the Hurricane could cary 12, albeit with the outer 4 spaced very far from the compact inboard 8 )

And round for round, comparing the "De Wilde" type incendiary .303 with the similar .5 vickers: the .303 weighs 9.8 g with .49 g incendiary content; the .5 Vickers round weighs 36.4 g with 1.94 g incendiary content. So roughly 4x the incendiary content along with longer range and better penetrating characteristics. (moderately higher velocity and significantly higher sectional density)

But, comparing the incendiary capacity alone (both had ~5% capacity, the vickers round weighed ~4x) it would take 10 .303 Brownings at 1,200 rpm (~100 lbs) to put the same weight of incendiary on target as 4x .5 Vickers at 750 rpm (at ~96 lbs). (note the 750 rpm figure was for the 1920's model, it may have improved by this time)


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## kool kitty89 (Nov 20, 2008)

For a propper destructiveness comparson (with Tony Williams' system) we need to compare the correct amunition with a similar mix as the one used on the .303 in Tony's table. (50% Incendiary with 50% of what apears to be ball) 
For the .50 this would give an average ammo destructive power factor of 3.6 (compared to 1 for the .303)
At 750 rpm this gives a gun power factor of 45. (compared to 20 for the .303, and 60 for the .50 BMG)


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## Glider (Nov 20, 2008)

Its an interesting debate but at the end of the day I still believe that the core of the problem for the RAF was the time it took to make the 20mm reliable. Had they done it on time its likely, indeed probable that the BOB would have been fought with 20mm armed Spits and Huricanes and most people who have praised the choice of the the 20mm.
They didn't, it was late and people have a tendancy to point out that the 0.5 HMG would have been a better choice.

Isn't hindsight a wonderful thing!!


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## HoHun (Nov 20, 2008)

Hi Renrich,

>I would like to hear from those in the know how the recoil from the various weapons load would impact the fighter. I have a reference that mentions that in a F8F if the cannons on one side had a stoppage it really introduced a yaw component.

Even a single machine gun jamming is described as having this effect in the P-51 manual. The advice to the pilots was to fire only short bursts if that happened and not try to compensate for the yaw by use of the rudder, which would not yield the required accuracy for shooting successfully.

Regards,

Henning (HoHun)


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## kool kitty89 (Nov 21, 2008)

Glider said:


> Its an interesting debate but at the end of the day I still believe that the core of the problem for the RAF was the time it took to make the 20mm reliable. Had they done it on time its likely, indeed probable that the BOB would have been fought with 20mm armed Spits and Huricanes and most people who have praised the choice of the the 20mm.
> They didn't, it was late and people have a tendancy to point out that the 0.5 HMG would have been a better choice.
> 
> Isn't hindsight a wonderful thing!!



This is quite true, and compared to the problems with the reliability of the US produced Hispano, the development was very timely. Of course, the US was in a somewhat better situation with their .50 gun available. 

That said the .50 in British service had other uses along side the 20 mm, basicly a replacement for all aplications still using the .303. (defensive armaments, suplemental armament to the 20 mm etc.)


It should also be noted that there were other choices for a decently performing cannon. Such that could enter service immediately in standard form and still have a fair margin of development potential which could be exploited in a shorter period of time than the Hispano was. (albeit without the potential of the later Hispano V)

Namely this one: ANOTHER MISSED OPPORTUNITY: THE OERLIKON FFL CANNON a weapon that had caught my interest for these qualities prior to finding this article. In its standard form it had significantly higher velocity (~750 m/s compared to ~600 for the FFF firing the same projectiles) with only a slight loss in RoF and moderate weight increase. (a good deal lighter than the Hispano -particularly the early versions- and a fair amount lighter than the High velocity -slower firing- FFS, while only slightly heavier than the .50 Browning)

Initially it would be drum fed (60 rounds like the FFF/ MG FF and the drum fed Hispano), but unlike the Hispano it could be easily mounted on its side in the wing. (with the drum next to it) Belt feed could then be introduced, and the Japanese demostrated that it could be sped up to ~750 rpm.

Also, due to the operating principal of the gun the recoil pulses were spread out in the firing cycle, resulting in less vibration, less stress on the airframe, and better stability while firing.


This weapon would also be suitable for flexible and turret mountings due to the compact size, weight, and good recoil qualities. (I immagine the drum feed would be preferred for flexible mountings)


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## r2800doublewasp (Nov 21, 2008)

Well didn't the British usually have four .303 cal. machine guns on each turret (like on the B-24) instead of two fiftys


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## kool kitty89 (Nov 22, 2008)

In some cases yes, but in other turets there were only two and in flexible mountings only one. And 2x .50's would still be more effective than 4x .303's. (depending somewhat to which .50 gun you compare, but for the US gun by a good margin, also true for the Vickers, but less dramatically)


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## KrazyKraut (Nov 22, 2008)

Lucky13 said:


> Which was the best aircraft fitted gun/cannon of WWII? And, why did the RAF stick with .303, what was their reasoning behind, why not go for bigger like .50's?



If you want one single answer it's either *MG151/20* or *Berezin B-20*. They both performed very solid against anything they encountered. They both fit on almost any plane and in a variety of positions and they both are noted for their reliability. In the end the B-20 looks best on paper, but I don't know if its chemical energy component is as good as with the 151 and Minengeschoss. To be fair it only entered the war very late, so overall its MG151/20 for me.


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## HoHun (Nov 22, 2008)

Hi Krazykraut,

>In the end the B-20 looks best on paper, but I don't know if its chemical energy component is as good as with the 151 and Minengeschoss. 

Here is a comparison of the muzzle power of various WW2 weapons. You'll see that the B-20 comes out at about half the power of the MG 151/20 per barrel:

MK 213/30: 9.55 MW
MK 108: 5.03 MW
MK 103: 4.08 MW
NS-37: 2.17 MW
MG 151/20 (MX): 1.4 MW
MG 151/20: 1.27 MW
Hispano V: 1.23 MW
VYa-23: 1.2 MW
Hispano II: 1.06 MW
37mm M4: 0.91 MW
MG-FF: 0.78 MW
20mm Ho-5: 0.71 MW
20mm ShVAK: 0.64 MW
Berezin B-20: 0.64 MW
Ho-1 / Ho-2: 0.64 MW
20mm Type 99-2: 0.63 MW
20mm Type 99-1: 0.52 MW
MG 151: 0.44 MW
12.7mm UB: 0.37 MW
.50 Browning M2: 0.28 MW
MG 131: 0.21 MW
Ho-103: 0.18 MW
12.7mm Scotti: 0.14 MW
Breda-SAFAT: 0.14 MW
Browning .303: 0.09 MW
MG 17: 0.09 MW

Unfortunately I'm unable to make a proper comparison to the MG 151/20 battery vs. battery as I don't have the ammunition weight data for the B-20 (cartridge weight plus weight of belting). If anyone has reliable data on this (or maybe just the cartridge weight), that would allow a better comparison! 

Regards,

Henning (HoHun)


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## kool kitty89 (Nov 22, 2008)

HoHun, those figures are for the kinetic energy figures only, without taking chemical content into account?

If you add chimical energy in it tends to skew things if you want to compare the merits of the guns. ([particularly if said guns were capable of using more destructive ammunition had it been available)

Also this tends to give an exageration of the destructive power, creating a much greater performance difference with increasing HE/I capacity than in Tony Williams' system. (which also uses momentum rather than energy)

Additionally the Ho-5 was capable of significantly better performance with the propper high strength alloys (used on early models), but lacking these the cartridges were significantly down-loaded dropping the ~830 m/s (for 112 g AP projectile) to only ~710 m/s.


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## HoHun (Nov 22, 2008)

Hi Koolkitty,

>HoHun, those figures are for the kinetic energy (or momentum) figures only, without taking chemical content into account?

No, they are for total power, including chemical content.

Regards,

Henning (HoHun)


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## vanir (Nov 22, 2008)

I'd like to add a document written by Sqn Ldr Ralph Sorley of Flying Operations 1 in the British Air Ministry.



> "The choice lay between the 0.303" gun, the 0.50" gun and a new 20mm Hispano gun which was attracting the attention of the French, and in fact of other countries in Europe who could obtain knowledge of it from them. During 1934 this gun was experimental and details of its performance and characteristics were hard to establish. On the other hand, designs of better 0.303" guns than the Vickers had been tested over the preceding years with the result that the American Browning from the Colt Automatic Weapon Corporation appeared to offer the best possibilities from the point of view of rate of fire. Our own development of guns of this calibre had been thorough but slow, since we were in the throes of economizing, and considerable stocks of old Vickers guns still remained from the First War. The acceptance of a new gun in the numbers likely to be required was a heavy financial and manufacturing commitment. The 0.50" on the other hand had developed little, and although it possessed a better hitting power the rate of fire was slow and it was a heavy item, together with its ammunition, in respect of installed weight...the controversy was something of a nightmare during 1933-34. It was a choice on which the whole concept of the fighter would depend, but a trial staged on the ground with eight 0.303" was sufficiently convincing and satisfying to enable them to carry the day."


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## vanir (Nov 22, 2008)

I'd have to hunt down the documentation, but I've also read the tremendous difference between MG FF types and MG151 both from pilot view and the receiving end.
Apparently the Oerlikon liked to tear large sections of airframe skinning away, but it had what pilots described as "sledgehammer recoil" (due to its origins not really being designed for aerial use), it felt like it was trying to tear the wings off when being fired, this seriously concerned many pilots. Mounted to fire through the engine vee, more recoil was absorbed by engine weight but it overheated and jammed frequently in this configuration.
By comparison the MG151/20 was an excellent gun with no complaints. On the receiving end it typically liked to punch small, fist sized holes through pretty much anything it hit: engine blocks, pilot armour, you name it.

From what I've read at Tony William's site the B-20 had a slightly higher rate of fire than the ShVAK and slightly better ballistics. The ShVAK is a very good weapon, either are probably as good as the MG151/20 on paper. I should look it up again, as it's been a while so I hope I recall this last, correctly and reflective of technical details. I'll get back to you with a link.


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## HoHun (Nov 22, 2008)

Hi again,

>Unfortunately I'm unable to make a proper comparison to the MG 151/20 battery vs. battery as I don't have the ammunition weight data for the B-20 (cartridge weight plus weight of belting). 

I found a cartridge weight (no belting) listed here:

ShVAK cannon - Wikivisual

Ignoring the weight of the belting, this gives the following rough comparison:

2x MG 151/20 (MX) - 187 rpg - 164 kg - 124% firepower - firepower per weight: 342%
2x MG 151/20 - 207 rpg - 172 kg - 112% firepower - firepower per weight: 294%
4x Berezin B-20 - 221 rpg - 264 kg - 113% firepower - firepower per weight: 193%
4x 20mm ShVAK - 221 rpg - 332 kg - 113% firepower - firepower per weight: 154%

So despite underestimating the weight of the Soviet ammunition a bit, neither the B-20 nor the older ShVAK (which fired the same ammunition as the B-20) compare too well to the MG 151/20.

The B-20 was an efficient gun, but it didn't have the powerful ammunition that was available for the MG 151/20, and this shortcoming affected the total efficiency of the battery negatively.

Regards,

Henning (HoHun)


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## kool kitty89 (Nov 22, 2008)

vanir said:


> Apparently the Oerlikon liked to tear large sections of airframe skinning away, but it had what pilots described as "sledgehammer recoil" (due to its origins not really being designed for aerial use), it felt like it was trying to tear the wings off when being fired, this seriously concerned many pilots. Mounted to fire through the engine vee, more recoil was absorbed by engine weight but it overheated and jammed frequently in this configuration.



That contradicts many things I've read. Firstly the Oerlikon FFF is derived from the WWI 20 mm Becker gun, designed for aircraft use. (the entire FF family was specificaly designed for aircraft use, with emphesis on wing mounting) The Oerlikon S and improved SS were used as AA guns and were more robust (heavier) versions of the FFS. Additionally the API blowback operating principal of the Oerlikon means that recoil is spread out throught the operating cycle, resulting in a smoother recoil pulse. The MG FF also used a less powerful amunition than the MG 151/20, so recoil should be even less by comparison.


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## vanir (Nov 22, 2008)

> (due to its origins not really being designed for aerial use)


Indeed this was a piece of speculation on my part. I've read Becker didn't originally design the gun for aerial use, but the aerial versions like the FF were descended variants. I put that together with the musings of an ex-Messerschmitt employee on pilot feedback about MG FF mountings.

Upon closer examination of technical details the API blowback system does appear a "softer" system than the short-recoil of the MG151. As you've outlined. Quite right.

Perhaps the concern was related to the light structure of early 109 wings, these were not originally intended to mount weapons and were modified for machine guns at RLM request (ref. Alfred Price).

My apolegies.


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## kool kitty89 (Nov 23, 2008)

You'd have to compare it to the characteristics of the underwing pod mounted MG 151/20's. (though this would only be an apromation as the mountings were different and the internal wing structure had been altered on later models as well)


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## HoHun (Nov 23, 2008)

Hi Vanir,

>it felt like it was trying to tear the wings off when being fired, this seriously concerned many pilots. 

I've never heard about that before. Where did you find it?

Regards,

Henning (HoHun)


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