# What was the air to air weapon, or combination of weapons, used in WWII?



## CobberKane (Aug 14, 2012)

The recent Spitfire XIV v P51D thread wandered for quite a while into the merits (or otherwise) of the Browning .303 used by the RAF throughout the war as opposed to the .50 beloved of the USAAF and USN. To broaden that discussion, what was the best air to air weapon of WWII? I’m talking out of historical context here – what single weapon type could best fulfil all the tasks faced by the various fighters of WWII; heaver bomber interception, fighter v fighter, the lot. Or alternatively, which fighter had the combination of weapons that could best cover all the bases. 4 X 20mm Hispanos? Eight X .50 brownings? Russian, American or Italian? Plenty of grist for the mill here…


----------



## DerAdlerIstGelandet (Aug 14, 2012)

It depends on the type of enemy you are fighting. 

Look at the evolution of the Luftwaffe fighters. When the Luftwaffe was on the offensive the armament was typically lighter. As the war progressed and Germany was having to combat the heavy bomber formations, the armament became more heavy. Of course more powerful engines probably had an influence as well. 

.303 and .50 are just fine for dealing with fighters. 

Basically I don't think there is a definative answer to this question.


----------



## CobberKane (Aug 15, 2012)

DerAdlerIstGelandet said:


> It depends on the type of enemy you are fighting.
> 
> Look at the evolution of the Luftwaffe fighters. When the Luftwaffe was on the offensive the armament was typically lighter. As the war progressed and Germany was having to combat the heavy bomber formations, the armament became more heavy. Of course more powerful engines probably had an influence as well.
> 
> ...



Undoubtedly, different armaments were used for different tactical situations throughout the war. 8x.303s were adequate for fighter vs fighter situations in the BoB, and marginal for bomber interception, whereas the German 30mm was better in the latter role than the former. What I’m thinking is, would one weapon set have done both jobs, if not as well, at least passably well? A quartet of Hispano 20mm a la Hawker Tempest perhaps, or the eight 'point fifties of the P-47? Or maybe tha La-7's trifecta of Russian 23mm? And what were the relative merits of those guns, or for that matter the various .50/12.7mm weapons fielded by the various powers?


----------



## parsifal (Aug 15, 2012)

Tony Williams has done an exceellent study on this issue. The linkis below

WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

Basically it wasnt just the mission that affected the best armament, it was also sometimes the pilots. Having a larger number of smaller weapons is better when your pilots are not as experienced. Heavier armament tends to be larger calibre, that in turn usually means a slower rof. Having a slower rof means you will generally need more deflection when shooting and this in turn required a higher skill level on the part of the shooter.

LMGs tended to be too light to hurt more heavily protected targets. Heavier cannon, like 30mm+ teneded to increase drag, weight and ammunition supply. They of course tended to affect performance as well.

IMO the best all round mix of armament was 4 x 20mm cannon. Good firepower, and range , but not so much weight and drag as to seriously affect performance. 

Who made the vest cannon? Id say the germans, whilst the US made the best HMGs. Id say the Brits were probably the best at fitting LMGs into the wings of fighters


----------



## Jabberwocky (Aug 15, 2012)

Tony Williams also did an article on the idea WW2 fighter armament:

IDEAL WW2 FIGHTER ARMAMENT

For those to lazy to read the article, his conclusion was that an ideal weapon for all but heavy bomber targets was a 20 mm cannon similar to a lightened Hispano Mk V, with electric priming and a sped up RoF (750 to 1000 rpm), firing slightly smaller and lighter ammunition (105 g vs the Hispanos 130 g shell), not too disimilar to a more streamlined German Minengeschoss round. Best mounting was in the wing roots, avoiding problems with harmonisation for wing guns, engine mounting with radials/some inlines and aerodynamic problems with cowl mountings. The cost is a 10% drop in RoF with electric priming. 

Personally, I believe the best LMG was the ShKAS (just shading the MG 17), best HMG was the UB 12.7 mm (Belgian FN Browning deserves a mention, despite the limited combat it saw), best 20 mm cannon is a tie between the Hispano Mk V and the B.20 and the best cannon over 20 mm was the MK 108. 

The Germans developed the best 20 mm + cannon ammunition with the thin walled Minengeschoss round for various calibers. The US developed the best HMG ammunition with the M8 API, although the Soviet API ammunition for the UB runs a VERY near second AND it was available several years earlier and the Italian and Belgian 13.2 mm HE rounds also deserve mention. Best LMG ammunition is a bit of a wash, although the DeWilde/Dixon ammunition for the .303 Browning deserves a mention, as does the Soviet 7.62 API and the b-patrone ammunition for the 7.92 x 57 guns. 

If I was going into combat, I'd want the Soviets designing my weapon, the Germans designing the ammunition and the installation, the US building and supplying it and the RAF servicing it and keeping it running.


----------



## CobberKane (Aug 15, 2012)

parsifal said:


> Tony Williams has done an exceellent study on this issue. The linkis below
> 
> WORLD WAR 2 FIGHTER GUN EFFECTIVENESS
> 
> ...


 
I was tending towards the 4 x 20mm formula myself; quick enough to hit fighters, big enough to hurt heavy bombers. But how did Hispanos stack up against the Russian Shvak or German MG151? I've read some claims that the Shvaks were the best of the lot. And I think the Germans were making some pretty hot ammunition for their guns towards the end of the war, significantly upping its hitting power.
Re the Browning .50, wasn't the German 12.7 a bit lighter and with a slightly higher ROF? Were the Italian Bredas any good? 
I'm more of a general knowlege kind of bloke than a techno-freak, so I'm happy to listen to more motivated individuals in these matters.
One other related question - where did the P-47 get its reputation for enormous fire power? Surely the RAF always had at least one cannon armed fighter in the line-up with more punch, before and after the 47 appeared.


----------



## parsifal (Aug 15, 2012)

Not an expert in thbis field, but I believe the Germans had explosive 20mm shells with enhanced ballisticsm, at least at the end.

Shvaks were not that good. They fired a lightweight shell, and had an rof below that of the German and allied equivalents.


----------



## Vincenzo (Aug 15, 2012)

Jabberwock, too me not a expert but i think that the "chemical" content of UB API ammo is larger of that of M8 API and UB had also HE and HEI ammos.

Parsifal, Shvak 20mm afaik is one of higher ROF 20mm of WWII


----------



## davebender (Aug 15, 2012)

However that only works with twin engine aircraft such as the Fw-187.

My second choice would be 1 x 3cm Mk108 cannon firing through the prop shaft. One hit does about as much damage as 4 x 20mm shells. Good only for close range but that's where most WWII era aerial kills were achieved. The Mk108 cannon has more killing power per pound of weight then any other WWII era fighter weapon. So even lightweight and dirt cheap aircraft such as the Me-109 and He-100 can pack a huge punch.


----------



## tomo pauk (Aug 15, 2012)

Hello, Dave,
For a fighter that can accept 4 cannons in the nose (but 23mm cannons), please see La-9 

My choice would be all Soviet, thank you  , even above 20mm bracket. With VJa 23 and NS-37 (if yours Shvaks are deemed as of too light a punch), one really has it all. P-38 with 4 VYas, in 1942, hmm...

Shvak was indeed firing one of the lightest shells, but it was doing it at high RoF (800 vs 600 of the Hispano II), and it was available way before any other belt fed 20mm cannon. Plus it was able to be synchronized, unlike the Hispanos (so a workable fighter with just 2 cannons was feasible good enough, not hampered with possible jamming of one of the cannons). Admittedly, the Mg-151/20 was the best package of the bunch, once introduced, up until B-20 was in town (enabling even the tiny Yak-3 to accept 3 of those in the fuselage).

added: being a necked up 12,7mm cartridge, Shvak's ammo took up the same volume for same number of rounds as it was the case for the Soviet 12,7mm rounds - enabling the Shavk to carry far more rounds, for the same allocated volume, than it would be possible for Hispano. (Too bad the Americans did not gave their .50s the same treatment of up-necking, it would've saved us of many internet debates  ) 
So, yes, Shvak was one great cannon.


----------



## Thorlifter (Aug 15, 2012)

davebender said:


> 4 x 20mm in the nose. However that only works with twin engine aircraft such as the Fw-187.



Didn't the La-9 have 4 nose mounted cannon's?


EDIT: Ahhhh, Tomo beat me to it.


----------



## renrich (Aug 15, 2012)

The 30 cal MG was not ideal or even adequate for dealing with fighters. The various 50 cals were. Probably the best all around weapon for air to air and air to ground including all AC was a reliable fast firing 20MM.


----------



## davebender (Aug 15, 2012)

I agree. For Soviet aircraft it was an excellent choice.


----------



## renrich (Aug 15, 2012)

Need to add that the 20MM cannon should have good velocity and good ammo capacity. The early war 20MM cannon in the Zeke had neither and was outclassed by the 50 BMG. I suspect the early 20MM in the BF109 was the same.


----------



## davebender (Aug 15, 2012)

Bear in mind we are shooting at aircraft 200 meters away. Large HE payload is more important then velocity at that distance.


----------



## renrich (Aug 15, 2012)

Not necessarily true that ranges are 200 yards. USN taught that fire was opened at 300 yards in full deflection runs and it you read Lundstrom there are many cases where Wildcat pilots opened fire in excess of 300 yards. It is my opinion that in order to get a decent understanding of all aspects of carrier warfare one would be well advised to read Lundstrom. "THe First Team" and "The First Team and the Guadalcanal Campaign." There is a lot more to fighter ops as well as attack ops from carriers than there is in landbased ops. A lot of remarks made by our members show that they regard good characteristics of various AC the same for landbased as well as carrier based. Taint so! The BOB 109s I believe carried 60 rounds of 20MM per gun just like the Zeke. You seldom read that that was a weakness of the 109 but it was a definite weakness of the Zeke. Firing time for naval carrier fighters was highly important because fighters were scarce and the fighters had to make up for lack of numbers by being more able to stay in the fight. That is the reason why the guys who operated the carrier air groups did not like the British mandated gun arrangement of the F4F4 with six guns and much the less ammo of the F4F3.


----------



## parsifal (Aug 15, 2012)

I think you are correct in assering that 200m was the norm for engagement ranges, or even kill ranges. Hartmann was legendary in being able to take out an enemy at extremely long range.

I tend to disagree however, that the F4F armament was somehow superior to the A6M2s. The first thing to note about the Zeke, was that later marks increased the ammunition supply, however that asside, we need to compare the characteristics of the two weapons and their fitment to their repsective mounts

F4F-3 had 4 x 0.5 mg with an ammunition supply of 430 rpg. That gave them a a firing cycle of 34 seconds. However, the F4F-3 was a very limited production run. Far more common was the the F4F-4 which had 6 x 0.5 in MG, but rpg was reduced to 240 rounds. this gave a firing cycle of less than 20 seconds

The A6M had 2 x 20mm cannon, each with 60 rounds. The Type 99-1 20mm cannon had a rof of 520 rpm and a firing cycle of just 7 seconds. They were at a definitie disdavantage in terms of firing times, however this was compensated for by the fact that 20mm rounds had stopping power of more than 4 times that of the 50 cal. That in turn meant the usual burst of the 20mm battery was reduced to less than a second, whereas, for the 50 cal batteries the usual firing cycle is about 3-4 secs. So long as the Japanese pilots retained a higher skills base than their American counterparts, they were not disadvantaged too much by the armemnt they were carrying.

As far as range was concerned, in my opinion that is a function of muzzle velocity more than anything. Again the 50 cal had some advantage, but not greatly so. The MV of the F4s armament was rated at 2900 f/s according to my source, whereas the Type 99-1 had an Mv of 1970 f/s. Over a 300yd distance to target, the different flight times is 0.31 secs for the 50 cal, whilst the Type 99-1 ammo would take 0.45 secs. If usual combat speeds are assumed to be 240 mph, the respective targets will have moved 39 feet in that 0.3 secs, whilst the Type 99-1 would have allowed its target to move 59 feet. thats another 20 feet. How much of a difference would that make? Some, of course, but is it worth sacrificing firepower to the extent of having 1/4 the firepower per gun? 

The other disadvantage that the F4F armament choice made was the weight of that armament. The f4F-3 had an all up armament + ammo weight of 512lbs. The F4F4 was carrying a weight of 420 lbs of armament + ammo weight. The Zero was carrying 176 lbs of armament + ammo (not inccluding the 7.7mm guns). This meant their armament was 34% that of the early marks Wildcat, and 42% that of the wing folding type. it was one of the reasons why the zero was so much more agile than the Wildcat, and why, IMO it was a superior mount.


----------



## CobberKane (Aug 15, 2012)

Thorlifter said:


> Didn't the La-9 have 4 nose mounted cannon's?
> 
> 
> EDIT: Ahhhh, Tomo beat me to it.


 
I think end of war versions of the La-7 had three nose mounted cannon. I guess the La-9 is disqulified by arriving post war, but I think at least some of them had four 23 mm cannon. Incidentaly, how much would synchronisation affect ROF?


----------



## Timppa (Aug 16, 2012)

Best air to air weapon, considering the ammunition, against 1-2 engined aircraft:
MG151/20 with Mine shell

Against heavy bombers:
R4M rocket


----------



## renrich (Aug 16, 2012)

F4F3-285
F4F3A-65
FM1-839 (four guns)
FM2-4437 (four gun)
For a total of 5691 Wildcats with four guns The Wildcat was around 29 feet long. A 20 feet mistake in lead can make a big difference. The ballistics of the two 7.7s in the nose were different from the 20MMs both in flight time and trajectory. The IJN pilots did try to limit use of the cannon to relatively close range because of rainbow trajectory. In the Thach weave, the wing man of the target would often open fire at ranges well over 300 yards, knowing that he only faced the puny 7.7s early. IMO mixed armaments were not as efficient as homogeneous armaments.
There were 1169 F4F4s, a few with four guns.


----------



## davebender (Aug 16, 2012)

BoB era Me-109s and Spitfires quickly ran out of fuel. 60 rounds might be enough for 15 minutes of combat. Aircraft that carry more internal fuel also need to carry more ammunition.


----------



## Shortround6 (Aug 16, 2012)

60 rounds was nowhere near enough for 15 minutes of combat. 60 rounds was good enough for 7-8 seconds of firing time after which the 109*E* had over 850 rounds of 7.9mm ammo _left_ for each MG 17. 

Spitfire MK Is carried about 17 seconds worth of ammo. 

A one second burst is pretty much useless for most pilots. One second _on target_ might be all it takes to inflect damage but it takes some time to get on target and around 1/3 to 1 second to stop firing at the end. Firing pilot realizes he is hitting _AND_ has inflicted enough damage takes a few tenths of second. The time of flight may be .3 or so? SO pilot is seeing damage (flames) with .3 sec worth of shells in the air and still has to release the trigger. The British were averaging about 17 shots per gun per burst from the Hispano guns near the end of the war. 60 shells is enough for 3-4 bursts. Maybe a fighter only gets 3-4 firing opportunities in 15 minutes, maybe it gets 4 firing opportunities in 2 minutes.


----------



## Shortround6 (Aug 16, 2012)

A few points about aircraft armament since "There Is No Such Thing As A Free Lunch". 

1. Light weight guns have to paid for either in low performance or low durability or both. 

2. Guns are not laser beams. they fire a "pattern" or group which gets larger with range. 

3. Most combat evaluations depend on an *AVERAGE*, some pilots do better or much better, some pilots do worse. Biasing armament too much one way or another has to be paid for. 

4. While looking at fighters with thousands (if not tens of thousands) built with minimal armament one also has to consider what was "wanted" but *not* fitted due to other considerations, like lack of space or lack of engine power. 

to elaborate a bit, take point #1. The US Browning .50 did the job in WW II but was far from ideal. It was heavy for it's power but the weight meant it was fairly reliable (the gun more than the feed mechanism/arrangements) and durable. Changing the barrel and a few minor parts might allow for a life of 10-20,000 rounds if not more. The Russian 12.7mm gun had a life closer to 2500 rounds. It was much lighter which allowed for higher performance of the planes carrying it. Many planes get shot down (or crash) well before reaching 2500 rounds fired. *BUT* many do not. B-17s or B-24s could easily fire 2500-5000 rounds from some of their guns in just 5-10 missions. Having to provide replacement guns in such numbers might be a problem. Having just one gun for most applications also simplified training of armorers, manufacture, supply of parts and ammunition. The US had the longest ( and perhaps the most complicated) supply lines of the major combatants of WW II. These "attributes" don't show up in a simple comparison of weights, rate of fire, velocity and projectile weight. The US was "blessed" with high powered engines and could afford better than most to use guns that were down on the weight/power efficiency scale. 

Point#2. in order to get lethal concentrations of fire at longer ranges ( and in aircraft longer range could be 400yds instead of 200 yds) more rounds per second are needed. Either higher rate of fire guns or more guns. You also have the time of flight problem which was mentioned by others. The US spent a considerable amount of time and money trying for even higher velocity than the .50 Browning had because they thought it would considerable increase the hit potential.

more later.


----------



## davebender (Aug 16, 2012)

> US spent a considerable amount of time and money trying for even higher velocity than the .50 Browning had because they thought it would considerable increase the hit potential.


So did Germany. The MG151/15 has to be one of the longest range machineguns ever made. 15mm x 96mm AP(WC) rounds achieved 1,030 meters per second.


----------



## Shortround6 (Aug 16, 2012)

davebender said:


> So did Germany. The MG151/15 has to be one of the longest range machineguns ever made. 15mm x 96mm AP(WC) rounds achieved 1,030 meters per second.



It would be a lot more useful in advancing discussions (instead of advancing an agenda) if you quoted general purpose figures instead of special purpose or limited issue ammunition ( or guns, as the case may be). 

There is some debate as to wither the MG151/15 is a cannon or a machine gun despite it's nomenclature. 

The 15mm x 96mm AP ammunition with the 1,030 m/s muzzle velocity is a APCR round with a weight of 52 g (compared to the 72g weight of the normal AP projectile) and it may not hold it's velocity or range as well as the normal ammunition. Most APCR did not. 
As for "one of the longest range machineguns ever made" it may have just a bit of trouble even matching the Czech ZB vz/60 (15mm BESA) let alone the Soviet 14.5mm gun. It rather depends on the actual shape of the projectiles involved. And that is for service guns. The US experimental cartridges which include the 20mm Hispano necked to .50 and .60 cal and the .60 cal case itself (later necked out to 20mm for the 20mm Vulcan gun) can both well exceed the German figures as can the Belgian commercial 15mm and 15.5mm commercial offerings. 
Not only were these American HV MGs extremely heavy for their hitting power ( being the size of or even larger than 20mm Hispano guns) but still using _non-exploding ammunition_ and they burned out barrels at an alarming rate. They traded higher likelyhood of hitting for the destructive power of 20mm shells once they had gotten a hit.


----------



## tomo pauk (Aug 16, 2012)

Re. Zero's armament: it was far away from the ideal set up, until it received belt fed, more powerful cannons. Same things apply as for the Bf-109Es.



CobberKane said:


> I think end of war versions of the La-7 had three nose mounted cannon. I guess the La-9 is disqulified by arriving post war, but I think at least some of them had four 23 mm cannon. Incidentaly, how much would synchronisation affect ROF?



Yep, three B-20 cannons were mounted in number of La-7.
La-9 simply serves as an example - 4 cannons (mostly/always in 23mm calibre?) in the nose were very much feasible for the ww2 technology.


----------



## parsifal (Aug 16, 2012)

> F4F3-285
> F4F3A-65
> FM1-839 (four guns)
> FM2-4437 (four gun)
> For a total of 5691 Wildcats with four guns



Which means these aircraft were all penalised by the extra weight of the wepons fit. A four gun broadside carrying 430 rounds is heavier than a 6 gun broadside carrying 240 rpg. 

An interesting aside. The RN tactics with the 6 gun broadside was generally not to fire all six guns simultaneously. The two outboard guns could be fired separately, as a result most FAA pilots used these two outboard guns as an emergency supply. RN was also first to develop LR tankage for the type, jury rigged by field mods in 1941. 




> The Wildcat was around 29 feet long. A 20 feet mistake in lead can make a big difference.


 I agree, but is it worth quatering you firepower per gun. I dont think that it does, and post war, most navies, including the USN tended to agree



> The ballistics of the two 7.7s in the nose were different from the 20MMs both in flight time and trajectory. The IJN pilots did try to limit use of the cannon to relatively close range because of rainbow trajectory. In the Thach weave, the wing man of the target would often open fire at ranges well over 300 yards, knowing that he only faced the puny 7.7s early. IMO mixed armaments were not as efficient as homogeneous armaments.



I agree, especially trying to marry two such dissimilar weapons as the 7.7 and Type 99-1. Might explain why the later marks of Zero partially chganged riflre mounted armament to 13.2mm guns. 




> There were 1169 F4F4s, a few with four guns.



Small correction. There were actually 1389, if the 220 Martlet IVs are included


----------



## Tante Ju (Aug 16, 2012)

Shortround6 said:


> Point#2. in order to get lethal concentrations of fire at longer ranges ( and in aircraft longer range could be 400yds instead of 200 yds) more rounds per second are needed. Either higher rate of fire guns or more guns. You also have the time of flight problem which was mentioned by others. The US spent a considerable amount of time and money trying for even higher velocity than the .50 Browning had because they thought it would considerable increase the hit potential.



All of these are contradicting requirements - a "lethal" concentration of fire requires the guns to have the least amount of spread, or exponentially increased number of rounds fired and rely on chance. Increasing muzzle velocity and general ballistic quality of gun WILL, on the other INCREASE the gun's spread exponentially on an automatic gun, means that the high velocity gun may have less time to travel to distance, but at the same time it will also score less hits because of greater spread, provided the aim point is correct. But if it's not, what is the pont of a supposedly long range gun, if you are just firing it off blind...?

Many did try out various guns with high ballistic capacity, but in the end everyone seem to have realize sooner or later the correct answer is to settle with a gun good enough for about 200 meters, and make it as light and fast firing as possible. See MG 151 -> MG 151/20, MK 103 -> MK 108, Hispano II -> Hispano V, Schwak -> B-20 etc.


----------



## DerAdlerIstGelandet (Aug 16, 2012)

Why does everyone always have to accuse everyone of having an agenda? Not trying to single anyone out here. It is just a common thing in these parts. 

Just discuss the topic and let the facts speak for themselves, whatever the facts may be.

In the end the facts and truth always come out...


----------



## Shortround6 (Aug 16, 2012)

Getting back to:

Point #3. a heavy armament ( in installed weight) benefits pilots who are poorer shots, have had less training/experience or are facing larger/heavier aircraft. Or combinations of the above. Depending on ammo supply the heavy armament can also provide longer firing times providing longer combat duration ( more intercepts/firing opportunities) per flight. It is payed for by poorer climb and maneuverability. A light armament gives the opposite, better climb and maneuverability but less combat duration and/or hitting power. With well trained pilots the light armament can be made to work against fighters and small bombers. But too heavy an armament for a given engine and the plane cannot get into firing position quickly or easily (if at all). It is all a trade off. 

#4. Ties in with the above. The Russians wanted more guns/ammo for the Lagg-3, Yak series but their inability ( for a number of reasons) to get more power from the 105 series of engines meant that heavier armament cut into performance too much.


----------



## Shortround6 (Aug 16, 2012)

tomo pauk said:


> Re. Zero's armament: it was far away from the ideal set up, until it received belt fed, more powerful cannons. Same things apply as for the Bf-109Es.



True.



tomo pauk said:


> Yep, three B-20 cannons were mounted in number of La-7.
> La-9 simply serves as an example - 4 cannons (mostly/always in 23mm calibre?) in the nose were very much feasible for the ww2 technology.



The B-20 weighed 25KG compared to the older ShVAK 20m canon weighing 42KG. The NS-23 weighed 37kg???
Armament (according to WIKI????) for an LA-7 was 2 ShVAK ( or B-20s?) with 200rpg or 3 B-20s with 100rpg.
The LA-9 with 4 NS-23 carried 75rpg?? 
LA-9 was a totally new airframe that just looked something like a LA-7. 
The LA-9 had tremendous firepower but it's combat duration was none too good. 8 seconds firing time?


----------



## CobberKane (Aug 16, 2012)

davebender said:


> BoB era Me-109s and Spitfires quickly ran out of fuel. 60 rounds might be enough for 15 minutes of combat. Aircraft that carry more internal fuel also need to carry more ammunition.


 
This seems to me to be the best characterisic of the .50s used in the P-51 and P-47. Either plane would have received a significant boost in firepower if fitted with cannon, but at the expense of ammunition load. The .50 was perhaps a bit over-hyped by might USAAF pilots who never had to face heavy bombers, but it was fine against single and twin-engined aircraft, reliable and enabled the Mustang and P-47, and especially the P-38, heaps of firing time - very important if you have to protect bombers of enemy territory for several hours


----------



## Shortround6 (Aug 16, 2012)

Tante Ju said:


> Increasing muzzle velocity and general ballistic quality of gun WILL, on the other INCREASE the gun's spread exponentially on an automatic gun,



Why? What would make the spread 4 times greater by doubling the muzzle velocity? 

It could happen but something sounds wrong with the set up. Weird barrel vibration, poor mounting, excessive "bouncing" or battering as the bolt goes back and forth. A lot of this can be "tuned" out. Wrong rifling twist for the projectile/velocity used? 



Tante Ju said:


> means that the high velocity gun may have less time to travel to distance, but at the same time it will also score less hits because of greater spread, provided the aim point is correct. But if it's not, what is the pont of a supposedly long range gun, if you are just firing it off blind...?


 Less time to travel the distance means that the aiming point is closer to the target. Before the deployment of good gyro gunsights (and radar ranging in Korea) the biggest problem in deflection shooting was figuring out the proper aiming point. The high velocity gun reduces this aim off error ( it does not eliminate it), a super tight grouping gun does no good if it is aimed at the wrong spot, it too, is being fired "blind". 



Tante Ju said:


> Many did try out various guns with high ballistic capacity, but in the end everyone seem to have realize sooner or later the correct answer is to settle with a gun good enough for about 200 meters, and make it as light and fast firing as possible. See MG 151 -> MG 151/20, MK 103 -> MK 108, Hispano II -> Hispano V, Schwak -> B-20 etc.



The last two examples are not really examples. Each pair uses the same ammo and for all practical purposes have the same effective MV and range. The MK V Hispano had 96.6% of the muzzle velocity of the MK II.


----------



## parsifal (Aug 16, 2012)

> The other disadvantage that the F4F armament choice made was the weight of that armament. The f4F-3 had an all up armament + ammo weight of 512lbs. The F4F4 was carrying a weight of 420 lbs of armament + ammo weight. The Zero was carrying 176 lbs of armament + ammo (not inccluding the 7.7mm guns).



We tend not to think about the weight penalties of a particular armament installation. Ive given those for the Wildcat and the Zero (and frankly was surprised that the F4F3 carried a greater weight penalty because of the additional ammunition carried. The F4F3 had a 34 second burst, which is not too bad. Somebody also said the Spitfire I had a 20 second burst. I havent cross checked that, but did find that the 8x 303s plus armament on the Spit amounted to 685 lbs. Thats quite a weight penalty for an armament even less lethal than the F4F, and worse, with even less burst time.

I wonder what the 109 weight penalties were .....


----------



## Shortround6 (Aug 16, 2012)

I am not sure where you got the 685lb figure for the Spitfire? 

See: Spitfire Mk IX Weights and Loading

439.5 lbs for eight .303s with 350rpg. MK I Spitfires had 300rpg? 

664lb for four .303s (and I added 14.5lbs to the weight in the chart) and two 20mm guns. 

A full load of .50cal ammo for a 4 gun Wildcat was 1720 rounds, which was 516lbs just for ammo (give or take depending on bullet type/belt mix) the four .50s weighed another 286lbs. Some Navy performance figures or weight charts show as little as 360lbs of ammo (300rpg?). The six gun version shows 433lbs for the guns ( different accessory than the 420lb weight? different solenoid or charging system? Not enough to worry about) with a _full_ ammo load of 1440 rounds or 432lbs of ammo. 


Fro your last question see: WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

and go to table 3. 

109E--------149KG
109F-4------129KG
109G-6/R6---286KG

I would note however that these weights are _*JUST*_ for the guns and ammo. as Tony's site says in the notes "It does not include belt links, ammunition tanks, gun mounting points and recoil buffers, synchronisation systems and trigger gear, et cetera. Realistic figures for the weight penalty would probably be 30 to 60% higher". 

as an example he gives the weights of a MK Vc Spitfire at 235kg (517lbs?) which should be the same as the MK IX table given above. Weights for Hispano guns are often given for the bare gun and do not include the belt feed mechanism and a few other bits and pieces, like the cocking/charging mechanism and firing system.


----------



## parsifal (Aug 16, 2012)

I found the information on a webpage do you think I can find it again....it had a green background. I dont mind being corrected, and take the point that we should compare apples to apples. Stanadard load out for the 303 in the A wing was 300rpg, as you say, so really to make our own comparison of "apples to apples" I would think we need to add up the weight of guns plus the ammo loadout. Foreget the other bits, all we are looking at are the guns and the bullets.


----------



## CobberKane (Aug 17, 2012)

I've got a couple of other points that I'd be interested to hear some views on

1. I understand that past a certain point the Spitfire was built with a 'universal' wing anble to house three armment options: 2x20mm+4x.303, 2x20mm+2X.50 or 4x20mm. Yet the first option seems to have been far and away the most common. Did the ability of the 20mms to bust holes in self sealing tanks and engine blocks then make the many small incendiary rounds from the .303 much more dangerous?

2. Is it true that one reason the Americans never really adopted the 20mm en mass was that the cannons they manufactured were less reliable then the British equivilents?


----------



## parsifal (Aug 17, 2012)

I found this discussion on Tony williams' site regarding the use of the 50 cal in US aircraft

"The end of 1941 also saw America and Japan enter the war. Their aircraft weapons were very different. America relied almost entirely on the Browning machine-gun, not just in .50 (12.7 mm) calibre, but, for the first couple of years, in .30 (7.62mm) as well. The Japanese army and navy air forces followed their own paths, the army steadily up-gunning from 7.7 mm through 12.7 mm machine-guns and later 20 mm cannon, with 30 mm and even larger guns seeing limited service by the end of the war. The navy started with a mixture of 7.7mm MGs and Type 99 (Oerlikon) 20 mm cannon and continued to rely on this cannon (initially the low-velocity Type 99-1, later the more powerful Type 99-2), although it did make some use of HMGs and was also introducing 30 mm guns by the end of the war. As in Germany, the destruction of American heavy bombers was a strong incentive for the development of weapons of 30 mm or larger calibre.

The Americans did not intend to make such a commitment to the Browning MGs. Both before and during the war considerable efforts were made to secure alternative aircraft guns. Trials of foreign equipment resulted in the selection of the 20 mm Hispano-Suiza HS 404, large numbers being made. The Browning-designed 37 mm M4 cannon was also introduced, although used almost exclusively by the Bell P-39 and P-63. However, the standard fighter armament became a battery of six .50 inch Browning M2 HMGs.

This has led to the often-expressed view that the .50 inch M2 was the best all-round fighter gun of the war. After all, the USAAF and US Navy fighters unquestionably came to dominate the skies in which they fought. If there had been a better gun, America would have used it. However, the truth is not quite as simple as that. There are two issues here; how good was the .50 M2 compared with other HMGs, and how effective was it compared with cannon?

The most obvious comparator was the Soviet UB, which fired ammunition of virtually identical power. The UB weighed 25 kg, compared with the M2's 29 kg, but the Soviet gun fired at 17.5 rps, compared with around 13 for the M2. In terms of power- to-weight ratio the Berezin was therefore clearly superior. The Browning fared better against most other HMGs, as they all fired less-powerful ammunition, so the M2 enjoyed advantages in range and penetration. However, it had a slightly lower rate of fire than the German and Japanese guns (both around 15 rps), and was also bigger and heavier. The most powerful of all of the HMGs was the 15 mm MG 151, but this was heavier and slower-firing than the M2. Overall, therefore, the .50 M2 was not the best of the HMGs but was about average, with reasonable performance for its weight.

How did HMGs compare with 20 mm cannon? The first problem is that the cannon varied hugely in size, weight and performance. The MG*FFM, Type 99-1 and B-20 were all lighter than the M2, but the first two were significantly worse in terms of muzzle velocity and rate of fire, although the B-20 matched the M2's rate of fire and was not far behind in velocity. The Japanese Ho-5 and Type 99-2 and the ShVAK and MG 151/20 were all somewhat heavier. Muzzle velocities and rates of fire were closer to the M2's but generally still not as good. The Hispano was significantly heavier and slower-firing until the British Mk V emerged near the war's end, matching the MG 151/20 in weight and rate of fire.

The foregoing compares only the guns' efficiency; it takes no account of ammunition, the area in which the HMG loses most ground. The 20 mm cannon shells were not only two to three times heavier than HMG bullets, but their HEI contents greatly increased their effectiveness. Although HE ammunition was available for most HMGs, their small bullets severely limited the quantity of chemicals carried, so the Americans decided not to use them. Initially, the M2 used a mix of incendiary and AP bullets, with some tracers, but in 1944 the M8 API began to take over. Rather curiously, this was based on the Soviet B.32 API used in the Berezin.

It is difficult to assess the effectiveness of different ammunition types, but various tests suggest that a typical World War Two-era HE or incendiary shell, with chemical contents forming about 10 per cent of total shell weight, was about twice as destructive as a plain steel shell of similar size and weight. This makes it clear that 20 mm cannon were considerably more destructive for a given total weight of armament than any HMG could hope to be. For example, the .50 M8 API contained less than one gram of incendiary, whereas the 20 mm Hispano SAPI achieved similar armour penetration but carried more than ten times as much incendiary material.

This advantage was recognised by the US Navy. After comparing the .50 M2 and the 20 mm Hispano they estimated that the cannon was three times as effective. In other words, the typical RAF armament of four 20 mm cannon was twice as destructive as the USAAF's six .50 HMGs, for very little more weight. Proponents of the Browning HMG point to its excellent ballistics, which enhanced its range and hit probability. But the Hispano's muzzle velocity was very similar, and although the blunt-nosed shells were less aerodynamic the difference over typical air-combat ranges was not significant.

The cannon's advantages are clearly shown in the decisions made as a result of combat experience by air forces with a choice of good HMGs and cannon. We have already seen how Germany preferred the 20 mm version of the MG 151 despite its poorer ballistics. In the 12.7 mm Berezin the Soviets had arguably the best HMG of the war, but they still preferred the heavier, slower-firing 20 mm ShVAK. Japan had several good HMGs available; the army's Ho-103, and the navy's 13 mm Type 3, a .50 Browning chambered for slightly larger-calibre ammunition, but they made increasing use of cannon.

So why did the Americans not make more use of cannon, specifically the 20 mm Hispano they already had in mass production? There were two main reasons. One was certainly that the M2 was adequate for its purpose. In Western Europe the main adversaries were fighters, which were much easier to damage and shoot down than bombers. In the Pacific Theatre the Japanese aircraft were initially poorly protected and easy to shoot down. Later Japanese aircraft were better protected, but again these were usually fighters. If the Americans had faced the need to stop raids by heavy, well-protected bombers, it is likely that the HMG's shortcomings would have been starkly revealed.

There was another reason, however, which explains why the US Navy, despite rating the cannon very highly and facing the need to deal with attacking bombers and kamikazes, fitted it to few aircraft. That was serious production prob*lems with the American Hispano, which gave it a reputation for unreliability. Despite production running well into six figures, the American Hispano failed to achieve an acceptable reliability standard for the duration of the war.

To return to the original question, were the Americans right to rely so heavily on the .50 M2 when all other combatant nations had a clear preference for cannon of at least 20 mm calibre? The answer has to be yes. It was adequate for its purpose, and was the only satisfactory aircraft gun in production in the USA. It was very reliable (except where the installations created problems), was made in huge quantities, and the simplification of supply by comparison with the diversity of weapons used by the Axis powers gave a major logistical advantage. However, the Americans could get away with using a weapon so deficient in destructive power not only because of the nature of their opposition, but also because the size and engine power of their fighters enabled them to carry a battery of at least six guns, thus making up in quantity what they lacked in destructive quality.

The advantages of the 20 mm Hispano M2 were not entirely ignored. It was carried by Lockheed P-38s, together with four .50 Brownings. It was also installed in nightfighters, which needed maximum firepower to convert a short firing opportunity into a kill. Four were installed in Northrop's P-61 Black Widow, and two could be mounted in a Grumman F6F-5N. The cannon's extra firepower was also appreciated for ground strafing.

After the war the US Navy quickly changed over to the 20 mm cannon in its improved, faster-firing and more reliable M3 form, but the USAF stayed with the .50 M3 until the fighting in Korea demonstrated once and for all that the HMG had had its day. From the mid-1950s the USAF at last replaced the old Browning with 20 mm cannon, initially the M39 revolver and then the M61 rotary - just as most of the rest of the world was moving up to 30 mm!"


----------



## Shortround6 (Aug 17, 2012)

parsifal said:


> I found the information on a webpage do you think I can find it again....it had a green background. I dont mind being corrected, and take the point that we should compare apples to apples. Stanadard load out for the 303 in the A wing was 300rpg, as you say, so really to make our own comparison of "apples to apples" I would think we need to add up the weight of guns plus the ammo loadout. Foreget the other bits, all we are looking at are the guns and the bullets.



.303 ammo seemed to weigh 6.64lbs per hundred rounds-belted. The links on RCMG ammo aren't too heavy so shouldn't be a big deal. difference in weight of ammo between 300rpg and 350rpg is 26.56lbs. 

We do have the answer for the often asked question of why not use four .50 guns on a BoB fighter. for the weight of eight .303s and 350rpg you get four .50 cal guns and 130rpg or just under 10 seconds firing time for 156lbs of ammo. .50 cal ammo is about 30lbs per hundred belted. for 17 seconds of firing time for four .50 cal guns the ammo weight is about 265lbs. 

I try not to get to excited about a difference of a few pounds, not all projectiles weighed exactly the same and as noted the guns themselves varied a bit due needed accessories (not including mounts, ammo boxes, heaters, etc). On the Hispano gun the belt feed mechanism was a separate assembly that could be unbolted from the gun, I am not sure if the gun could easily be converted back to drum feed. But this extra "assembly" could help explain the difference between the "nominal" weight of the Hispano and the installed weight. 
It is when the weight differences get to the 100-200lb range that things begin to get important. 

The P-47 seems to be the champ of WW II single engine fighters with 613kg worth of guns and ammo ( at 425rpg which it did _not_ carry often when hauling large underwing loads?)


----------



## Shortround6 (Aug 17, 2012)

CobberKane said:


> 2. Is it true that one reason the Americans never really adopted the 20mm en mass was that the cannons they manufactured were less reliable then the British equivilents?



It is true, one of the major differences was the American guns had a chamber that was just a fraction of an inch ( a millimeter or 2) longer than the British guns. This did not provide enough support when the firing pin struck the cap, allowing the cartridge to slide forward cushioning the firing pin strike and causing misfires.


----------



## renrich (Aug 17, 2012)

The AAF had a reason in WW2 for liking the 50BMG over cannon. They felt that it improved the chances for the average pilot to get hits. The USN felt differently.
At Midway, the Wildcats in the CAP were undoubtedly handicapped by the shorter firing time of the F4F4. Even with the diminished performance of the F4F4 there were several times that CAP Wildcats over the Yorktown got in position to interecept IJN Attackers but were already out of ammo. One could almost make a case that Yorktown would have survived if the Wildcats had had the amament of the F4F3.


----------



## parsifal (Aug 17, 2012)

> At Midway, the Wildcats in the CAP were undoubtedly handicapped by the shorter firing time of the F4F4. Even with the diminished performance of the F4F4 there were several times that CAP Wildcats over the Yorktown got in position to interecept IJN Attackers but were already out of ammo. One could almost make a case that Yorktown would have survived if the Wildcats had had the amament of the F4F3




But that is not really supportable. The f4f-4 could, as the RN had found, be used in such a way as to extend the firing time of the armament, not reduce it. by switching off the outer guns, they could have 4 x 0.50in guns firing 240 rounds and 2 x 0.50 in guns also with 240 rounds. That gives a sequential firing cycle of 480 rounds, as opposed to 430 in the f4f-3. Moreover, the f4F-4 suffered less weight penalty from its armament compared to the F4f-3. What the f4f4 gave up to possess that additional firing time, was reduced firepower at least for the second half of the weapon discharge.

What probably caused the USN problem was the use of all six guns simultaneously. that most certainly would reduce the firing cycle.

However that cannot be laid at the feet of the f4f4. if anything, the type gave the pilots the option of either increasing their firepower for a shorter period, or, having the same firepower for a shorter period of time, and a reduced amount of firepower that when considered with the four gun broadside, actually extends the overall firing cycle. And it does that for no weight penalty.

i would say the USN was lucky that the f4F4 was developed. They probably misused it, but that is not the fault of the aircraft.


----------



## renrich (Aug 17, 2012)

It may not be supportable but it is what the USN said. I believe I will take their word on it. The majority of the people in the USN that operated the F4F4 did not like the six gun package at all, did not like the downgrade in the performance from the F4F3. That is why some late model F4F4s mounted four guns and the subsequent FMs used four guns. Don't believe me. Read Lundstrom!


----------



## tomo pauk (Aug 17, 2012)

> Shortround6 said:
> 
> 
> > The B-20 weighed 25KG compared to the older ShVAK 20m canon weighing 42KG. The NS-23 weighed 37kg???
> ...


----------



## renrich (Aug 17, 2012)

I misspoke in the above post. I said that the majority of the navy did not like the four gun package on the F4F4. I meant the six gun package and later corrected my misstatement. Must be my old age. I apologise.


----------



## parsifal (Aug 17, 2012)

its fine ren, and Im not disrespecting the USN either, or at least, not meaning to.


----------



## renrich (Aug 18, 2012)

In Lundstrom, " The First Team," There is a whole chapter of the book ,#18 called "Midway Lessons- The F4F4 Controversy" In the chapter it is related how the Navy told Eastern that the eleventh production FM1 must revert to the four gun package and the result with some other small changes was a 500 pound lighter AC. Interestingly, the early F8Fs carried only four M2 50s.


----------



## parsifal (Aug 18, 2012)

If the marks of the Wildcat that followed the F4F4 were lighter, it was not because of reverting back to the 4 gun broadside, and retaining or restoring the ammunition supply to 430 rounds. A four gun broadside with 430 rpg is 334 lbs heavier than a 6 gun broadside with 240rpg. 50 cal ammo weighs a ton, for no explosive effect. 

These later versions either reduced the ammo supply or achieved their weight reductions by other means.


----------



## oldcrowcv63 (Aug 19, 2012)

parsifal said:


> If the marks of the Wildcat that followed the F4F4 were lighter, it was not because of reverting back to the 4 gun broadside, and retaining or restoring the ammunition supply to 430 rounds. A four gun broadside with 430 rpg is 334 lbs heavier than a 6 gun broadside with 240rpg. 50 cal ammo weighs a ton, for no explosive effect.
> 
> These later versions either reduced the ammo supply or achieved their weight reductions by other means.



My math doesn't agree with yours at all. The way I figure it, the result of deleting 2 x 0.5" HMGs and adding a total of 280 rounds per gun comes out to be a net weight reduction of about 60 pounds. The aircraft loses 144.3 pounds deleting the two fifties and gains 84 pounds adding 280 rounds of ammo. -144 + 84 = -60. What have we done differently? Values are from America's 100,000.

In general, I think the relative desirability of cannon armament is quite different in the PTO vs the ETO. In the PTO fighting aircraft with unprotected fuel tanks, incendiaries are quite satisfactory surogates for the chemical explosions obtaned using cannons. 6 x 50s are probably close to a bare minimum in the ETO while 4 HMGs were found to be fairly effective in the PTO. 

With respect to weight and ammo supply, there is nothing but the precedent of the F4F-3 to determine the amount of ammo a 4-gun F4F-4 carried. Such an A/C could lose 740 rounds and still have more ammo per gun (and longer firing time) than an F4F-4. That would be a total weight reduction of about 275 pounds. My impression (and I am hoping Rich Leonard stops in for an informed opinion) is that the whole get-me-home reserve for USN pilots was something rarely used in combat. What apparently worked over time was training in marksmanship and gunnery discipline. There were a fair number of ace-on-one-mission created using the F4F-4 which to me is quite astonishing considering the brief firing time compared to the F4F-3.

Reading first person accounts, I see (perhaps unwarranted in truth but an impression I have) the word "burst" in describing a pilot firing at an an enemy more frequently replaced by the word "squirt" as the war progressed. Is that an indication pilots were learning to cope with the 18 seconds firing time? Beats me.

I am very much in agreement with Renrich that the F4F-4 6 gun suite probably cost the USN two aircraft carriers (Yorktown and Hornet).

PS I am not advocating 250 rpg for a modified F4F-4, but something between 240 and 430 rpg might have provided the extended firing time pilots wanted and a small improvement in the climb-rate that would prove beneficial for a carrier based interceptor defending its homeplate. By comparison, IIRC, the F2A carried 325 rpg. Other USAF fighters I believe carried lesser amounts.


----------



## parsifal (Aug 19, 2012)

oldcrowcv63 said:


> My math doesn't agree with yours at all. The way I figure it, the result of deleting 2 x 0.5" HMGs and adding a total of 280 rounds per gun comes out to be a net weight reduction of about 60 pounds. The aircraft loses 144.3 pounds deleting the two fifties and gains 84 pounds adding 280 rounds of ammo. -144 + 84 = -60. What have we done differently? Values are from America's 100,000.
> 
> In general, I think the relative desirability of cannon armament is quite different in the PTO vs the ETO. In the PTO fighting aircraft with unprotected fuel tanks, incendiaries are quite satisfactory surogates for the chemical explosions obtaned using cannons. 6 x 50s are probably close to a bare minimum in the ETO while 4 HMGs were found to be fairly effective in the PTO.
> 
> ...



Ive made a mistake in the math, but the F4F4 is not 500 lb heavier due to its armament.

The weight of the Browning M2 HMG is 83.78lbs. The weight of the 0.5in round is 4.09 ounces, give or take. For this excercise I am just looking at the weight of the armament + weight of the ammo carried. 

For the F4f4 that is (6 x 83.78lbs) + (4.09x6x240/16 lbs) = 502.68 lbs + 368.1lbs = 870.78lbs

For the F4f3 that is (4 x 83.78lbs) + (4.09x4x430/16 lbs) = 335.12 lbs + 439.68lbs = 774.79lbs

That makes the F4F4 96 lbs heavier than the F4F3. thats a long way short of 500 lbs, even if my crappy maths is embarrassing.

However, the other elements of my point still stands. The F4F4, if used in the same way as the RN was using them (and the USN had six months to avail itself of that methodology prior to Midway) actually had a few seconds longer in terms of firing cycle (about 10 seconds longer in fact), so the alleged loss of two carriers can in no way be laid at the feet of the extra guns carried by the F4F4. The USN had a choice in the way it used these fighters, and chose to use them in a certain way. That choice may be argued as being a factor in the loss of the two carriers,. not the superior capabilities of the F4F4. 

The F4F3 is credited with having a 34 second firing cycle. That equates to an rof of 750 rpm. At that rate, the (4 x 240) +(2 x 240) has an overall firing cycle of about 40 secs, compared to 34 secs in the F4F3. However, if all six huns are used simulataneously, the firing cycle is reduced to about 20 secs. 

I cannot see how flexibility causes the loss of carriers, and disagree with Lundstrom because of that 

The reduced performance of the F4F4 is unarguable...it had a lower top speed and a poorer rate of climb. however what is being overlooked in that assessment is that it (the F4F4) was based on the Martlet IV, which had specified wing folding with the wings folded aft rather than up. I acknowledge that later F4F3 also came with wing folding, but they were developed after the pioneer work had been done with the martlets and F4F4s. Moreover, the martlet IV could carry an extra 58 gallons of fuel compared to the F4F3, and this gave it vital range and endurance advantages.

Sure the F4F4 had penalties, but relatively few of those vices can be attributed to the weight of the armament, or the reduced firing cycle. Plus, the gripes about performance dont take into account that more a/c could be carried as a result of those penalties, and that a/c could operate for longer in the air.

I would suggest the F4F4 is being used as a scapegoat to cover the real mistakes made in an otherwise incredible victory


----------



## oldcrowcv63 (Aug 20, 2012)

Wow, where to begin... I think we agree that the F4F-4 was not heavier than the F4F-3 simply as a result of the two fifties. Lundstrom by citing Jimmy Flatley, actually endorses the F4F-4. To appreciate the argument about the loss of the two carriers you should read Lundstrom if you haven't already done so, and read it very carefully and try to put yourself in the cockpit from a situational awareness perspective, which Lundstrom, not being a pilot, perhaps found difficult leaving the matter to simply recounting the events as described to him. This to his credit. I think you may be misunderstanding what's being said here. I do not think anyone is saying replacing the F4F-4 with -3s is preferable. I certainly don't think that.



parsifal said:


> Ive made a mistake in the math, _*but the F4F4 is not 500 lb heavier due to its armament.*_
> 
> The weight of the Browning M2 HMG is 83.78lbs. The weight of the 0.5in round is 4.09 ounces, give or take. For this excercise I am just looking at the weight of the armament + weight of the ammo carried.
> 
> ...



Crappy math forgiven of course... But only if you forgive mine when next I make a similar mistake. which I inevitably will (and I taught math). 

I think your numbers are fairly accurate based on comparison with those I used from AHT and other sources. I don't think you're saying that the F4F-4 was actually only 96# heavier but rather merely citing what can be attributed to the guns and ammo. Correct? 

The wing fold was absolutely necessary. As you've suggested, the debate about the wisdom of the extra two guns isn't just about firing time but a combination of firing time and performance. I can't say for certain how USN fighter pilots managed their guns. Although, considering the letters written to their leaders and BuAer by many, it was a _*movement *_that drove the latter to remove them from the FM-1, but by then it was probably an irrelevant or inconsequential modification. USN Fleet CVs were no longer being defended by Wildcats. 



parsifal said:


> However, the other elements of my point still stands. The F4F4, *if used in the same way as the RN was using them* (and the USN had *six months to avail itself of that methodology prior to Midway*) actually had a few seconds longer in terms of firing cycle (about 10 seconds longer in fact), so the alleged loss of two carriers can in no way be laid at the feet of the extra guns carried by the F4F4. The USN had a choice in the way it used these fighters, and chose to use them in a certain way. That choice may be argued as being a factor in the loss of the two carriers,. not the superior capabilities of the F4F4.



Well, at Midway, the squadron pilots actually only had about 2 months to adapt in the case of the Enterprise and Hornet. Less for the Yorktown's VF-42 which only received its F4F-4s days before the battle and was by far the most heavily engaged of the VF's afloat at Midway. For the Hornet, I get the impression that firing discipline and marksmanship had adjusted to the change and the loss of the Hornet was more related to performance although the pilots were more critical of the firing time. Reading Lundstrom, who gives a detailed description of the CAP battle, I have come to the conclusion that the -4's lackluster climb was the culprit more than lack of firing time. Lundstrom does not agree with me on either count. 



parsifal said:


> The F4F3 is credited with having a 34 second firing cycle. That equates to an rof of 750 rpm. At that rate, the (4 x 240) +(2 x 240) has an overall firing cycle of about 40 secs, compared to 34 secs in the F4F3. However, if all six huns are used simulataneously, the firing cycle is reduced to about 20 secs.
> 
> I cannot see how flexibility causes the loss of carriers, and *disagree with Lundstrom* because of that



I may have forgotten, but I don't believe Lundstrom ever said that. You are unfortunately peering at Lundstrom through a disavowed acolyte. Flexibility, if it comes with the price of diminished interceptor performance (which is the primary function) is too expensive.



parsifal said:


> The reduced performance of the F4F4 is unarguable...it had a lower top speed and a poorer rate of climb. however what is being overlooked in that assessment is that *it (the F4F4) was based on the Martlet IV*, which had specified wing folding with the wings folded aft rather than up. I acknowledge that later F4F3 also came with wing folding, but they were developed after the pioneer work had been done with the martlets and F4F4s. Moreover, the martlet IV could carry an extra 58 gallons of fuel compared to the F4F3, and this gave it vital range and endurance advantages.
> 
> Sure the F4F4 had penalties, but relatively few of those vices can be attributed to the weight of the armament, or the reduced firing cycle. Plus, the gripes about performance dont take into account that more a/c could be carried as a result of those penalties, and that a/c could operate for longer in the air.



My understanding of the history here is that the USN was promoting a wing folding F4F version, and the FAA jumped on board. If that is not the case please give me references as so many of mine suggest the former. AFAIK, the later F4F-3s were built as trainers and not deployed as combat a/c.



parsifal said:


> *I would suggest the F4F4 is being used as a scapegoat to cover the real mistakes made in an otherwise incredible victory*



No, it's a matter of detailed post-battle analysis whose source is mainly pilots post-battle debriefing. No doubt, Midway was an incredible victory. Santa Cruz, a possibly avoidable defeat. 

The increase in firing time by the get-me-home-reserve strategy may have foundered when pilots were trying to kill the one aircraft they were sure would kill their carrier. That's the aircraft that is, at that moment, in your sights. Reserving two of your guns may extend your firing time but, when the first ones are out of ammo and you are down to using the two remaining guns, the probability of a kill may be cut in half.


----------



## oldcrowcv63 (Aug 20, 2012)

WRT Firing discipline at Santa Cruz. Two aces-on-a-single-mission were created during the CAP battle: George Wrenn (5 kills) and Stanley Vejtasa (7 kills).


----------



## oldcrowcv63 (Aug 20, 2012)

Should have added Scott McCusky as probably the earliest ace-on-a-single-mission for Midway in an F4F-4. 

Also I am not disputing that the first Martlet IIs were produced earlier than the F4F-4.

In fact, I was surprised to find (Thanks to RCAFson) that the initial batch of non-folding wing Martlet IIs (which subsequently became identified as Martlet III variants. This gets confusing quickly) were just F4F-3s with the -76 P&W engine. 

It appears these FAA _F4F-3s_ Martlets came off the Grumman production line in late 1940! I am wondering if THEY ever went to sea on a RN carrier?


----------



## renrich (Aug 20, 2012)

Please don't blame Lundstrom for any assertion that Yorktown was lost because of six gun F4F4s. As far as I know he made no such assertion. I said that that a case could be made that Yorktown was lost because the Wildcats carried too little ammo. It would not be a very good case either. Lundstrom's chapter on the F4F controversy only details all the remarks by the USN BUAER and the pilots and even some of the admirals. There are some mysteries about F4F weight losses and gains. Dean in AHT tries to explain them but there are many variables and the guns and ammo are only part of the issue. I wanted to quote the data from AHT which seems to me to be the best reference on that particular subject but it is too complicated.

In one graph in AHT the Overload Fighter gross weight for the F4F3 and F4F4 were as follows:
F4F3 over load fighter gross weight-7543 pounds
F4F4 overload fighter gross weight-7972.5 pounds


----------



## oldcrowcv63 (Aug 20, 2012)

As you say, definitely not Lundstrom's position Ren, the weight numbers for the F4F-4 and FM-1 are indeed contradictory or inconsistent at best. There are a variety of sources that say the two aircraft were essentially identical except for the guns and ammo supply, yet if you look (in AHT for one example source, at the empty weights the F4F-4 and FM-1, the former jumps for no apparent reason from a weight of 5,778.9# to 5,895#. The empty weight of the FM-1 is listed as the larger number. There is no breakout table to explain this difference. This discepency appears in other sources as well and I've never seen it justified. Complicating things is the implicit suggestion in AHT that the F4F-4 had the OPION to dispense with two of its 6 50s. That is also something I've never heard.


----------



## Shortround6 (Aug 20, 2012)

If you look at the tables in AHT and in the the specification sheets posted on Spitfire performance you will find the navy had the _"option"_ of deleting 2 guns from from both the F4F-3 (leaving two guns) and the F2A (not listed in Spitfire performance) for certain missions or for certain conditions. 

How the "Brass" in their US shore offices viewed things vs how the flyers and carrier officers viewed things (especially once shots were fired) are two different things. The guns could be pulled for maintenance, they were not _sealed into_ the wing so they certainly could have been pulled on the F4F-4 if the flyers/group commanders had wanted to. I don't know if there was a different wing rib or some other problem that would prevent bigger (longer) ammo boxes from being fitted for the four remaining guns. Given the resources available to a carrier (on board machine shops) I doubt that the fabrication of ammo box extensions would have posed an huge problem if the air-group commander and Ship Captain really wanted them. 

Perhaps the doors/hatches in the wing for reloading the ammo were smaller on the 6 gun fighters than the 4 gun making it too hard to place the belts in without causing kinks or potential feed problems?


----------



## oldcrowcv63 (Aug 20, 2012)

There is a comment that always puzzled me about the 6 gun rig. At least one source says, "When we saw how Grumman had modified the aircraft to accommodate the 6 guns we were very dissatisfied. I always assumed it was the third wing gun being placed so far outboard of the first two. There may have been an element of the design that prompted (Non-FAA  ) customer disapproval.


----------



## Shortround6 (Aug 20, 2012)

I can't find pictures of the real thing but pictures of models show:

F4F-3








F4F-4






real F4F-4





While they might let mechanics and crewmen build new ammo boxes cutting new doors in the top of the wing might be frowned on


----------



## zjtins (Mar 11, 2013)

I find much of the info to date misleading. Comparing energy of chemical (explosive) vs mechanical is pointless. The do not have the same affect on a target. 

A .50 solid bullet can destroy a water cooled engine in 1 shot. A 20mm thin shelled round may explode on the engine's surface and essentially do nothing. 

A .50 cal bullet can punch a .50 hole through Aluminum skin and do nothing, a 20mm thin walled shell can strip whole sheets of skin off a target aircraft when the aircraft is moving at high speed.

Many of the write ups to date are too simplistic.

There are several important categories that must be considered that a round needs to deal with, air vs water cooled engine, self sealing vs non sealed fuel tanks, small vs large aircraft (or lightweight vs robust). Also important are pilot or other armor, and round dispersion (based on distance to target and, gun positions and muzzle velocity/round drag). 

In the Pacific 6x.50 cal in the wings was perfectly acceptable to shoot at non sealed fuel tanks and unarmored aircraft. Very few bullets and the plane was in flames
In the Europe 6x.50 cal in the wings also worked enough. And the P-47 damage reports with its 8 fifties were never questioned.

But 4x20mm the FW-190 and other aircraft used were also very effective. May of the Russian aircraft used 1 or 2, 20-23 mm centerline (or near to) in their fighters and found them to work on German aircraft. 

Also many of the expert German pilots found the 1x 20mm center line to work well for them.

The .30 cal was universally scoffed at but in the beginning (BOB) 8 per aircraft was standard in England. They would use typically half there load to bring down 1 German but it worked. 

Before a serious comparison can be made the conditions must be understood. 
Shooting down a Zero vs B-17 are not the same in terms of gun needs. I have seen reports of many pilots taking down 3, 4, 5 even 7 Japanese aircraft in 1 battle. The best the Germans ever did was 2 B17's no matter what armament/airplane they used (in one battle). 

When asking the question we must make sure the comparison is valid when the results are in.


----------



## Shortround6 (Mar 11, 2013)

There can be a big difference between "works", "works well", and "works really well". 

There is also a big difference between what would _FIT_ in some cases and what was _WANTED_. The Soviet aircraft being a big case in point. Many Soviet aircraft with the 20mm though the prop hub were tried with various combinations of Machineguns in the cowl. two 7.62s, one 12.7, one 12.7+ one 7.62, two 12.7. The Russians (like everybody else) kept looking for more firepower but their low powered engines prevented the use of the heavier gun combinations as the performance penalty was too great. With the LA-5 and radial engine there _may_ have been a CG issue. The change from two 20mm guns to three 20mm guns only coming about when a lighter 20mm gun was introduced (along with fewer rounds per gun) to keep the armament installation weight about the same. A single 20mm + MG/s "worked" but they were not happy with it and tried a number of alternatives to it.

There is also a big difference between what works for an "expert" and what works for the vast majority of rookies. Too much emphasis on "it works for Ace Blankety-Blank, it should be good enough for you rookies" means you have an awful lot of rookies who are a whole lot less effective than they could have been. 

Between the US. 50 cal and the British 20mm Hispano the 20mm was the more destructive/effective weapon. Especially for the installed weight. Which cost more to make ( one 20mm=two .50s??) I don't know. The .50 was easier to maintain. the .50 suffered fewer stoppages. The .50 fit in places the 20mm wouldn't (like turrets). 

The .50 did the job, that doesn't mean it was the best choice.


----------



## zjtins (Mar 15, 2013)

Best choice is limited to all limitations, cost , production capability, power, accuracy, reliability, ammo availability, weight....
Many of the spit had 2 20mm and 4 .30 cal. The ME109 had 1 20mm and 2x 8 or 13 mm MG. The P-47 had 8 .50 Cal all others had 6 (basically).

The MGF or Oerilkon was slow, low rate of fire, and not reliable. Yet this was used or copied for most of the war until others were developed because they had it. The Brits could not move to a .50 cal cause they had no production base. They actually had a .60 cal in development just before the war but dropped it to maximize production on existing weapons for what soon came to be the BoB. 
The best example of 20mm use was the FW190 4xmg151/20 (not the 2 MGFF version). That seemed to really work well. 

Also later the US went to 20mm x4 or vulcan later due to range over the .50 cal. Today the US is moving the 25mm for even more range.


----------



## Gixxerman (Mar 15, 2013)

The Mosquito combo of 4 x 20mm cannons 4 x .303 machine guns always seemed a very deadly brew to me.


----------



## tomo pauk (Mar 15, 2013)

zjtins said:


> Best choice is limited to all limitations, cost , production capability, power, accuracy, reliability, ammo availability, weight....
> Many of the spit had 2 20mm and 4 .30 cal. The ME109 had 1 20mm and 2x 8 or 13 mm MG. The P-47 had 8 .50 Cal *all others had 6* (basically).
> 
> The MGF or Oerilkon was slow,* low rate of fire, and not reliable*. *Yet this was use door copied for most of the war* until others were developed because they had it. The Brits could not move to a .50 cal cause they had no production base. They actually had a .60 cal in development just before the war but dropped it to maximize production on existing for what soon came to be the BoB.
> ...



By 'all others' you presume some of US fighters?
The 90% of Hispano cannon RoF still does not qualify as low rate of fire. Any good data about the (I presume) MG-FF being not reliable?
Care to elaborate what does "Yet this was use door copied" for someone whose 1st language is not English?
British Vickers was selling abroad their .50in guns ammo prior the war, there was other things what made the .50 cal not that appealing for the British. For the Hispano their production base was also equal to zero pre-ww2, they geared pretty fast for that one.
Any good data about British .60 cal in development?


----------



## Denniss (Mar 15, 2013)

Never really heard of reliability problems with MG FF or MG FF/M, at least nothing I could remember having read of.


----------



## Greyman (Mar 16, 2013)

tomo pauk said:


> Care to elaborate what does "Yet this was use door copied" for someone whose 1st language is not English?



I think he meant to type 'used or copied'.


----------



## tomo pauk (Mar 16, 2013)

Yep, Greyman, that seems to be that. So the MG-FF or Oerlikons were being "used or copied for most of the war until others were developed because they had it". That description fits to all of (not only) ww2 weaponry: one use or copy (or the other way around, plus designs, produces...) one thing until he does the same with a next, hopefully better thing.


----------



## yulzari (Mar 16, 2013)

The British .303 Browning choice was governed by a desire to use existing huge stocks and production lines of .303" ammunition as used by the army as well. Also by a belief that future combat would only give the briefest of moments when the guns could be brought to bear. Hence the cheap choice of a sort of airborne shotgun of x8 .303". At the same time they knew their weakness against armour, heavy engine castings and self sealing fuel tanks and that these would be the coming things. The research had shown that .5" rounds could not carry effective HE so the next step up they took was to seek the introduction of 20mm cannon and the pre war specification was for a 4 cannon fighter which went into production as the Westland Whirlwind and the Bristol Beaufighter. These used 60 round drums and the RAF already knew this was a restriction and were investigating belt feed versions as the war began and these became the new norm by 1942 and allowed the single engined fighters to fit 20mm cannon into wings designed for .303".

So the RAF went through the whole issue of this thread before the Battle of Britain and found battle experience only confirmed the pre war policy of multi .303" to be superceded by 20mm.

The production advantages of the .303", both in supply and existing gun manufacturing resources, did keep the multi .303" alive into 1942 with x12 .303" machine guns going into the Hurricane II and being designed by Martin Baker for the nose of the Whirlwind. The latter being a real airborne shotgun with 20 rps giving 240 rps in a circle of fire of less than a metre across when aligned straight ahead. That could saw off a wing or fuselage even if it could not penetrate armour. Nevertheless it was only a temporary measure until the 20mm cannons could be made in enough numbers to be the standard.

Had the RAF needed to defeat heavy bombers post 1943 then I suspect we would have seen a rerun with 20mm cannon increased to x6 while the 40mm S gun was developed into a belt feed, possibly for high speed twin engined fighters or jets. Post war the threat of Soviet B29 (apologies Tu-4) heavy bombers was being met with the development of 30mm rotary cannon using German experience.


----------



## J.A.W. (Mar 17, 2013)

British NF Mosquitos armed with 4 close grouped 20mm Hispano cannon showed they were well able to bring down heavy bombers - He 177s in the Operation Steinbok/Baby Blitz `44, sans drama, P61s were armed with those too, to good effect [ plus some had another 4 .50s in a turret].


----------



## zjtins (Mar 25, 2013)

Sorry about the typos, I will try to clean them up before I post. 
The MG FF reliability was relative to the use and other weapons (particularity the MG151/20 for comparison). The Oerlikon based weapon relied on a heavy external spring. G loading, wear, dirt, sprig quality (particularly in Japan)all caused problems, also the fed mechanism was problems initially it was only fed by drum. Attempts later took a a while to get a belt feed model reliable.

One of the reasons (not the only one) for the ME109E to switch from the twin cannon to the single cannon F models, was the gun stoppage on one side caused real problems in fighting. If reliability was not an issue then this would not have been a factor. 

Some issue I have with some statements will continue as real world experience never meets with simple testing or analysis.

A 1 meter spread on the ground rapidly becomes 2,3, 4 or more in a fight. With the guns synchronized at a given distance, any deviation from that distance between two planes rapidly increase the dispersion. And since the best attack is to pounce someone (highs relative speed from behind) that affect seemed to be very significant. Loss data seems to indicate the 8x.303 were not very good, generally most of Brits aces (BoB) were getting 1 or two a day coming back low or no ammo. 

Also low dispersion does not mean a hit, it means more rounds on target assuming the average is on target, the difficult part.


----------



## tomo pauk (Mar 25, 2013)

zjtins said:


> Sorry about the typos, I will try to clean them up before I post.
> The MG FF reliability was relative to the use and other weapons (particularity the MG151/20 for comparison). The Oerlikon based weapon relied on a heavy external spring. G loading, wear, dirt, sprig quality (particularly in Japan)all caused problems, also the fed mechanism was problems initially it was only fed by drum. Attempts later took a a while to get a belt feed model reliable.
> 
> One of the reasons (not the only one) for the ME109E to switch from the twin cannon to the single cannon F models, was the gun stoppage on one side caused real problems in fighting. If reliability was not an issue then this would not have been a factor.
> ...



I'll again ask for definitive stoppage values, or at least creditable data re. MG-FF reliability. The 'oerlikons' were designed as drum-fed weapons, stating that it took a while to convert them to belt feed have no bearing on drum-fed versions. The MG-FF was a stop gap, until the MG-151 could be worked up to be a viable weapon.


----------



## zjtins (Mar 26, 2013)

I will try to find the references. 



> I'll again ask for definitive stoppage values, or at least creditable data re. MG-FF reliability



Same can be said about assuming they were equal in reliability, where's the proof?


----------



## tomo pauk (Mar 26, 2013)

You've stated that 


> The MGF [=MG-FF]or Oerilkon was slow, *low rate of fire, and not reliable.*


Yet, despite being asked 3 times, you did not bothered to support that claim (in bold) by any means. So I'll politely ask you to post some facts that can support your claim


----------



## zjtins (Mar 26, 2013)

> You've stated that
> The MGF [=MG-FF]or Oerilkon was slow, low rate of fire, and not reliable.
> Yet, despite being asked 3 times, you did not bothered to support that claim (in bold) by any means. So I'll politely ask you to post some facts that can support your claim


I will when I can find one. Read this a long time ago before the internet.
And just because I can or cannot find a reference does not make the assumption they were the same any more valid.


----------



## tomo pauk (Mar 26, 2013)

You have fired a lot of duds, apart form the 'oerlikons' having issues. Let me remind you (bolded words):



zjtins said:


> Best choice is limited to all limitations, cost , production capability, power, accuracy, reliability, ammo availability, weight....
> Many of the spit had 2 20mm and 4 .30 cal. The ME109 had 1 20mm and 2x 8 or 13 mm MG. The P-47 had 8 .50 Cal *all others had 6 (basically)*.
> 
> The MGF or Oerilkon was slow, low rate of fire, and not reliable. Yet this was used or copied for most of the war until others were developed because they had it. *The Brits could not move to a .50 cal cause they had no production base. They actually had a .60 cal in development just before the war but dropped it to maximize production on existing weapons for what soon came to be the BoB. *
> ...



What is the American proverb? Put your money where your mouth is? 



> Same can be said about assuming they were equal in reliability, where's the proof?





> And just because I can or cannot find a reference does not make the assumption they were the same any more valid.



Who are 'they', and at that part of 'them' I was claiming anything, let alone something I cannot prove?


----------



## zjtins (Mar 27, 2013)

They as in the two weapons.


> What is the American proverb? Put your money where your mouth is?



I am merely asking for the same information you are of me. Cite some reference that shows the reliability of the two weapons are the same, otherwise that is an assumption not a fact.


----------



## tomo pauk (Mar 27, 2013)

Okay, so 'they' means MG-FF and MG-151.
If it's not too much a problem for you, could you please quote my claim about reliability of MG-151 (especially relative to MG-FF) that I need to back up with reliable data. In the mean time I'll patiently wait for you to shed some light about the claims from post #61 of this thread.


----------



## Matt308 (Mar 27, 2013)

Easy guys. Don't let this get out of hand.


----------



## zjtins (Mar 27, 2013)

Your claim is that you say (and keep assuming) they are the same and demanding I come up with a reference to say they are not. If you make no claim then there is no discussion, we can agree that my claim is in fact valid. 

Asking someone for proof is by definition an assertion their claim is false, ergo your claim. 

All things being equal my claim they were not have the same reliability is as valid as yours, until one of us comes up with a valid reference. 

Problem is this came from reading a book before the internet, so I have to figure out what I read and try to find it. That's probably not going to happen immediately but I will keep trying.


----------



## Glider (Mar 27, 2013)

I admit that I was not aware of any serious reliability issues with the 20mm FF type of weapon and believe that it was down to more than the gun. How it was mounted was as important, if not more so.


----------



## zjtins (Mar 27, 2013)

> I admit that I was not aware of any serious reliability issues with the 20mm FF type of weapon and believe that it was down to more than the gun. How it was mounted was as important, if not more so.


Exactly my point, looking at gun and round specs do not tell the whole store thank you.


----------



## zjtins (Mar 27, 2013)

See this thread for info on MG FF problems. #305
http://www.ww2aircraft.net/forum/weapons-systems-tech/20mm-cannon-best-worst-specs-comparison-lmg-hmg-etc-29624-21.html#post999846

And as someone else pointed out on the FW-190 you cant stick a 151/20 round in the _MG FF_ it blew up.

Sorry MG FF/M


----------



## tomo pauk (Mar 27, 2013)

Thanks for the effort to provide proofs.
The 1st link does not work, it opens the generic, 'ad powered' web site. About the quoted text from the post #305 there:



> MG FF/M:
> 
> The MG FF/M was a motor cannon with 20 mm caliber. This gun was manufactured in Germany under licence, but it was developed by Oerlikon in Switzerland. The MG FF/M was 1338 mm long at a weight of 26,3 kg. The cadence of this weapon was 540 rounds per minute at max, the speed, the projectiles got, leaving the muzzle was 700 meters per second.
> The cartridge had a weight of 202 g, 134 g apportioned to the projectile. The ammunition was stored in magazines.
> ...



The quoted text does nod discern the MG FF and MG FF/M. Their ammo was not interchangeable. 
MG FF/M was developed and produced by Ikaria, Berlin. It was not a motor cannon, it was being installed in many different parts of the airframe; it took time for Germans to have it as a working motor cannon. The 'FF' meaning 'Flugel fest', ie. 'suitable for wing'.
The weight of the shell fired by MG FF/M at 700 m/s was 92g. The MV of the shell that weighted 134 g, fired by MG FF, was 600 m/s. The sentence 



> Deployed by the Luftwaffe in 1935 it soon became obsolete, because the penetration was not enough to destroy the heavy allied bombers anymore.



is a gem on it's own, incorrect on all accounts: MG FF/M was deployed by Luftwaffe in 1940, not in 1935; the ww2 cannons were not machine guns (to depend on penetration to destroy bombers), they were using shells (depending on explosive shrapnel effect instead); the MG FF/M was used as 'Schraege musik' in Bf-110 night fighters to kill heavy bombers.
The MG FF was never installed in Bf-109D and F; the F-0 got the MG FF/M. 

With all that said, should we believe author's words that MG FF/M often jammed, it's shells broke etc? Where is the assessment of the MG FF reliability?



> And as someone else pointed out on the FW-190 you cant stick a 151/20 round in the MG FF it blew up.



The Fw-190 got the MG FF/M, not MG FF, sorry for nitpick. It was not the fault of the MG FF/M design that a later design had the similar round, and surely it was not it's fault that a member of the ground crew was filling the drum with wrong round. 
Until you can back up the claim that such things were happening, that statement goes into the same shelf with statement that XP-39 was making 400 MPH, Bf-109G1 making 700 km/h, XP-40Q being base for P-51, ie. in the shelf with other myths.

You might want to start with this post, Anthony (Tony) Williams is world expert on this:

http://www.ww2aircraft.net/forum/we...nons-machineguns-topic-6368-3.html#post235948


----------



## tyrodtom (Mar 27, 2013)

If you look at the different 20mm rounds the MG-FF/MG-FFM 20x80 with a rim diameter of 19mm, and a case diameter of 22mm, compare that with the round fired by the MG-151/20, 20x82, rim diameter of 25.2 mm, and a case diameter of 25.2mm. 
When you think of those dimensions, and look at pictures of the two different rounds, there's no chance of even the a idiot of a ground crewman putting a MG-151/20 round in a MG-FFM magazine, you couldn't beat it in with a hammer. Plus the cartridge case of the MG-151/20 is so much bigger there's no way it would even partly go into a MG-FFM's breech.


----------



## Denniss (Mar 27, 2013)

The only problem I heard of with the MG FF series as an ammo feed problem in the drum under high G load but nothing more, not even close to the "problems" claimed by this site.
More MG FF related errors from this site: it was not directly produced under license, Ikaria got a license for the Oerlikon FF F (itself developed from the german Becker gun). The MG FF was developed further to use a larger/longer cartridge for improved performance. The projectile weight is wrong, 134g is for the FF, not FF/M, 540 rpm and ~700m/s was only possible with HE/M rounds in the FF/M


----------



## tomo pauk (Mar 28, 2013)

The quoted article also forgets another main user of the MG FF/M, namely the Fw-190, that was using it from late 1941 until late 1943.


----------



## Shortround6 (Mar 28, 2013)

it was also used in a bunch of Bf 110s, and in He 111s and a few Ju 88s and other aircraft for ground strafing and shipping attacks.


----------



## tomo pauk (Mar 28, 2013)

Indeed. 

Further, the MG FF/M, with 700 m/s MV for the M-geshoss was indeed not a 'fast' cartridge, but one could not say it was that slow, either. The MV was about 85% of MG-151/20, and almost 95% of ShVAK. Not bad for 28 kg cannon.


----------



## zjtins (Mar 28, 2013)

Yah a I had to use the cached page the website had connection problems, I thought it was me. 

The MG FF/M is the same basic gun as the FF modded for the minegeshoss cartridge my bad wrong reference.

Its a translated page... the FF was deployed in 35 in Spain, does not talk about the FF/M introduction.


----------



## zjtins (Mar 28, 2013)

They use the shrage musik upward with a MG FF/M or M108 as they fit the MG 11/20 was too difficult to fit.
Later that added short tube with 30mm minegeschoss since they would only get 1-2 passes.

The 20mm was left in some of the night fighters as the would have more time on target. 
Late the Germans were trying 37mm, 50mm, and even a 75 mm for one shot kills as the likelihood of a fast mover staying on target to get rounds on targets for the older weapon was not happening. 

A problem with this discussion is what target? what time during the wa? what assumed pilot experience? which round? which setup (inline vs wing) which gun (Brit, German, Russian...) they all impact the results.


----------



## tomo pauk (Mar 28, 2013)

zjtins said:


> Yah a I had to use the cached page the website had connection problems, I thought it was me.
> 
> The MG FF/M is the same basic gun as the FF modded for the minegeshoss cartridge my bad wrong reference.



Okay. 



> Its a translated page... the FF was deployed in 35 in Spain, does not talk about the FF/M introduction.



Prior the S. civil war, how plausible is that Germany would deploy an airborne cannon, that was being in prototype stage? The S.C.W. started in 1936. A weapon 'expert' , from the page you've posted, that does not discern between MG FF and MG FF/M is not someone I'd trust on the matter, anyway.



zjtins said:


> They use the shrage musik upward with a MG FF/M or M108 as they fit the MG 11/20 was too difficult to fit.
> Later that added short tube with 30mm minegeschoss since they would only get 1-2 passes.



The weapon worked, it had a decent RoF, MV, was compact light, and, most importantly, fired a destructive shell. Seem like a logical choice for 'Shraege musik' to me.



> The 20mm was left in some of the night fighters as the would have more time on target.



Care to elaborate?



> Late the Germans were trying 37mm, 50mm, and even a 75 mm for one shot kills as the likelihood of a fast mover staying on target to get rounds on targets for the older weapon was not happening.



I'd really like to see some reference the LW airborne, bomber-busting 75mm cannon. It was used only against ground targets IIRC. The experiments with weapons bigger than 20mm should imply that LW found the MG 151/20 was not ideal for bomber busting.



> A problem with this discussion is what target? what time during the wa? what assumed pilot experience? which round? which setup (inline vs wing) which gun (Brit, German, Russian...) they all impact the results.



I'm sure most of the forum members would agree that such variables should dictate the wepon set-up. The problem of this discussion was a number of unsubstantiated claims?


----------



## zjtins (Mar 28, 2013)

From wiki.... Just saw this



> In the dual-purpose vehicle mount, the M2HB (heavy barrel) proved extremely effective in U.S. service: the Browning's .50 caliber AP and API rounds could easily penetrate the engine block or fuel tanks of a German Bf 109 fighter attacking at low altitude,[30] or perforate the hull plates and fuel tanks of a German half-track or light armored car.[24][31][32]


----------



## zjtins (Mar 28, 2013)

> I'm sure most of the forum members would agree that such variables should dictate the weapon set-up. The problem of this discussion was a number of unsubstantiated claims?



Only claim I am making is the 6 or 8 x .50 cal setup was effective enough and roughly equal to the 4. x 20mm of WWII. I keep getting drawn into side conversations. 

As for unsubstantiated where is substantiation that the 4x.20mm setup was significantly better than the 6 or 8x .50 cal in WWII?

I have never seen anything from anyone, on this forum or in all my literature readings. 

It is an assumption until someone bring proof or data or something other that the 20mm round is bigger that the .50 cal.


----------



## zjtins (Mar 28, 2013)

More info I am not going to copy it, its the whole thread. 



> AIRCRAFT PERFORMANCE COMPARISONS.... HOW AND WHY WE COMPARE THEM


----------



## tomo pauk (Mar 28, 2013)

zjtins said:


> *Only claim I am making* is the 6 or 8 x .50 cal setup was effective enough and roughly equal to the 4. x 20mm of WWII. I keep getting drawn into side conversations.
> As for unsubstantiated where is substantiation that the 4x.20mm setup was significantly better than the 6 or 8x .50 cal in WWII?
> I have never seen anything from anyone, on this forum or in all my literature readings.
> It is an assumption until someone bring proof or data or something other that the 20mm round is bigger that the .50 cal.



I'll 1st apologize to the forum members for boring them wit repetition.
Let me remind you about the claims, post #61 in this thread: 



> Best choice is limited to all limitations, cost , production capability, power, accuracy, reliability, ammo availability, weight....
> Many of the spit had 2 20mm and 4 .30 cal. The ME109 had 1 20mm and 2x 8 or 13 mm MG. The P-47 had 8 .50 Cal all others had 6 (basically).



All others have had 2 cannons + 2 MGs, or just 2 MGs, or a cannon and 1-3 pairs of MG, or 3 cannons, or 4 MGs....



> The MGF or Oerilkon was slow, low rate of fire, and not reliable.



Proof?



> Yet this was used or copied for most of the war until others were developed because they had it.



Copied because they had it?



> The Brits could not move to a .50 cal cause they had no production base.



They were producing .50 cal Vickers, and they have had no production base for Hispano, yet went for it.



> They actually had a .60 cal in development just before the war but dropped it to maximize production on existing weapons for what soon came to be the BoB.



Any proof about British .60 in gun?



> The best example of 20mm use was the FW190 4xmg151/20 (not the 2 MGFF version). That seemed to really work well.



Okay.



> Also later the US went to 20mm x4 or vulcan later due to range over the .50 cal. Today the US is moving the 25mm for even more range.



Proof that range was/is the reason? 
By 'proof' I mean that you post information(s) made by credible people, like Tony Williams, Emanuel Gustin, Christian Koll and like, ie. the book authors owners of creditable web pages. A member of this forum (nick 'Charles Bronson') has several threads about the aircraft guns in the Weapons sub-forum, that might be a good start also. The person mixing the different German guns would be the bad start. 
I won't go to the claim about timeline of MG FF and Spanish C.W.


----------



## zjtins (Apr 2, 2013)

Go read the referenced thread, then go argue with them.


----------



## tomo pauk (Apr 2, 2013)

In other words, opinions of the forum's members (and they disagree in almost all topics touched there) are now a reference?



> then go argue with them.



???


----------



## Shortround6 (Apr 2, 2013)

I skipped around few pages but when I hit the one where they were arguing about trucks I gave up.


----------



## zjtins (Apr 4, 2013)

> I skipped around few pages but when I hit the one where they were arguing about trucks I gave up.



So you read only what you want to reinforce your own opinion but refuse to read what might trigger you to change your own mind. That's called myopic thinking.


----------



## Jabberwocky (Apr 4, 2013)

zjtins said:


> Only claim I am making is the 6 or 8 x .50 cal setup was effective enough and roughly equal to the 4. x 20mm of WWII. I keep getting drawn into side conversations.



Which runs contrary to the conclusions of both armament experts of the period - of all nations - and present day experts. 

A single 20 mm cannon is estimated at having an effectiveness of anywhere from 2.5 .50 cals to around 3.5 .50 cals, depending on the cannon itself and ammunition fired. 

So, a 4 x 20 mm set up would be roughly equavilent in firepower to ten to 14 .50 cals, for roughly the weight of six .50 cals.



> As for unsubstantiated where is substantiation that the 4x.20mm setup was significantly better than the 6 or 8x .50 cal in WWII?
> 
> I have never seen anything from anyone, on this forum or in all my literature readings.
> It is an assumption until someone bring proof or data or something other that the 20mm round is bigger that the .50 cal.



Read Tony William's website and articles for a start: WORLD WAR 2 FIGHTER GUN EFFECTIVENESS
IDEAL WW2 FIGHTER ARMAMENT

You could also look at the proceedings of the Joint Fighter Conference in the US.


----------



## Jabberwocky (Apr 4, 2013)

zjtins said:


> More info I am not going to copy it, its the whole thread.



What the sweet fanny adams is that?

Having read through the whole, mildly mis-informed thread, there were perhaps a half dozen posts on comparing the .50 cal and the 20 mm. In the first page and a half. And then, nothing at all.

You're lambasing posters for "myopic thinking", but obviously haven't read your own links.

Shameful.


----------



## Shortround6 (Apr 4, 2013)

zjtins said:


> So you read only what you want to reinforce your own opinion but refuse to read what might trigger you to change your own mind. That's called myopic thinking.



No, it means I am too lazy to wade through over 100 pages of a Forum thread to try to find what you were too lazy to pin point better. Like page numbers or reply numbers. 

I have tried to give a few sources or use easily found references, It shouldn't be too hard to find the F-89 or other US fighter types on the internet.


----------



## Readie (Apr 5, 2013)

The Browning .303in gun could be found in the vast majority of British bombers. It was used in many Frazer-Nash turrets, such as the FN-5, which was used in both the Wellington and Lancaster bombers. In contrast, the Americans used .50in machine guns in their bombers, while fighter aircraft were increasingly using 20mm cannon.

The Browning Mark II did have some important advantages. It was reliable, accurate, and available in large numbers. The longer range of the heavier guns was more useful in daylight operations, and was of little benefit at night, at least until radar assistance was available for gunners. The heavier calibre guns also used heavier ammunition – the .303 bullet weighed 0.4 oz, the .05 more than three times that much at 1.4 oz. The use of the heavier gun forced a reduction in potential bomb load, or in the amount of ammunition carried.

Ammo or bomb load?
The article makes an interesting point about night operations
Cheers
John


----------



## Shortround6 (Apr 5, 2013)

The weight difference was actual much worse. A loaded .50 round weighed about 5 times what a .303 or .30 round did. 

The .50 could somethings very well but neither it or it's ammo were light in weight.


----------



## CobberKane (Apr 5, 2013)

I think the USN/USAF perseverance with the .50 in preference to cannon armament had sound basis in logistics and the weapons effectiveness for the work at hand ; interception of aircraft up to the size of medium bombers. However, this does not mean the fifties represented the level of destructiveness of 20 mm cannon. The conclusion of the USN was that one 20mm was worth about three .50s. The navy went to cannon after the war, the airforce did not, and the armament of the F 86 in Korea has often been cited as a weakness.
The .50 was/is an excellent weapon, but there is a reason heavy machine guns largely disappeared from fighters after the war. Explosive cannon shells were almost universaly seen as the way to go.


----------



## Shortround6 (Apr 5, 2013)

The other thing with the US .50 was it was about the _heaviest_ .50 cal/12.7-13mm MG in service. The Russian 12.7 which more powerful and fired faster was lighter. ALL the rest of the _common_ 12.7-13mm guns were much less powerful and except for the Italian guns, much lighter. 
The later American planes had the engine power to lug the .50 battery and ammo around. Some of the more common American fighters in 1942 can lay _some_ of their poor performance at the .50 cal door ( or the insistence on using SIX guns)


----------



## zjtins (Apr 9, 2013)

> Which runs contrary to the conclusions of both armament experts of the period - of all nations - and present day experts.



I keep hearing this mantra but no combat data to support it. Like I said before you can analysis the round or gun by themselves but a round cant fly. A 30mm minegeshoss beats all on paper but the ROF and MV limited the value.  Ralls comment was he thought he could watch the B-17 fly between the rounds when he shot. 

I added just 1 link of many German aircraft being shot down in under 1/2 sec of fire. I see no comment on how a 20mm setup would have markedly improved on that. I see no real discussion as to why US did not switch to a 3 times better weapon. At that rate 2x20mm = 6x.50 call so the fighters would only have to carry 2x20mm and been lighter for it. So explain that, why not change? Somewhere this 20mm setup being so much better argument falls apart. Again the .50's were good enough (.5 sec burst = fight down) and the US had a production base.


----------



## Glider (Apr 9, 2013)

Your entire case seems to depend on films. You ignore any research and rely on your own reading. You also ignore the fact that the films only show the aircraft that got away. When asked for evidence you just post references back to the films.
If the evidence of the war was based on films, Germany won the war hands down as they had the best film propaganda

Re this comment _added just 1 link of many German aircraft being shot down in under 1/2 sec of fire. I see no comment on how a 20mm setup would have markedly improved on that_. You ignore the evidence of the Spitfire written off by four hits in non critical areas, four hits that with a 0.5 would have done nothing.

and this _So explain that, why not change? Somewhere this 20mm setup being so much better argument falls apart_ you know the reply, the 1942 US 20mm guns and their ammunition were very unreliable, that for the USAAF the 6/8 x HMG were good enough but were not good enough for the USN. You ignore the fact that the USN were very keen for the 20mm.

and this _A 30mm minegeshoss beats all on paper but the ROF and MV limited the value _ you ignore the fact that the Mk 108 had the same ROF as the 20mm Hispano II (10 rps) and was very similar to the 0.50 HMG (13 rps) 

You say it was range but produce nothing to support it. You ignore the fact that 20mm were mainly fitted on NF's who fight at close range. You ignore the written views of the fighter conference which debated this very point from both USN and USAAF.


----------



## zjtins (Apr 9, 2013)

> Re this comment added just 1 link of many German aircraft being shot down in under 1/2 sec of fire. I see no comment on how a 20mm setup would have markedly improved on that. You ignore the evidence of the Spitfire written off by four hits in non critical areas, four hits that with a 0.5 would have done nothing.



So 1 picture of spit is worth more than dozens of fighter shot down???



> You ignore the fact that the USN were very keen for the 20mm.


They were so keen they built almost 20,000 aircraft with 20mmm as front line fighters. Whats your point. Mine is the .50 cal setup was sufficient. I might to the point where an alternative was not a priority until after the war. A classic example or wartime priority would be fixing our non exploding torpedoes. That received top priority once the head guy got out of the way and pentagon finally believed the numbers. It was solved in short order then. The 20mm never got this attention. So the NAVY being keen deos not translate into planes shot down, combat performance. Being keen is not a combat result.




> and this A 30mm minegeshoss beats all on paper but the ROF and MV limited the value you ignore the fact that the Mk 108 had the same ROF as the 20mm Hispano II (10 rps) and was very similar to the 0.50 HMG (13 rps)


 I am lost on your point here, I did not ignore anything here, my point is shell size alone does not translate into better combat performance. a larger slower shell with limiting ROF = not a very effective weapon system. Basically that was Ralls opinion, loved the ME262 did not think much of the 4x30mm. 



> You say it was range but produce nothing to support it. You ignore the fact that 20mm were mainly fitted on NF's who fight at close range. You ignore the written views of the fighter conference which debated this very point from both USN and USAAF.


Hence they only used it on night fighter= short range... my point thanks


----------



## zjtins (Apr 10, 2013)

> You also ignore the fact that the films only show the aircraft that got away



No I see them and also see they are not taking hit near center mass. You don hit something is does not matter what round you are using. An yes I have seen 20mm hits on wings and tail and fuselages. Again Bob Johnsons book show many 20mm hits and the planes still came home.


----------



## Glider (Apr 10, 2013)

zjtins said:


> So 1 picture of spit is worth more than dozens of fighter shot down???


Yes, as it proves that the 0.5 had to hit a critical area wereas the 20mm didn't. Something you do not deny


> I might to the point where an alternative was not a priority until after the war.


For the USN it was a priority during the war


> So the NAVY being keen deos not translate into planes shot down, combat performance. Being keen is not a combat result.


Being keen is wanting a better combat result because you need a better combat result.


> I am lost on your point here, I did not ignore anything here, my point is shell size alone does not translate into better combat performance. a larger slower shell with limiting ROF = not a very effective weapon system. Basically that was Ralls opinion, loved the ME262 did not think much of the 4x30mm.


The point is simple the 30mm mk 108 had a very good ROF, it did have a slower shell with less range but it had a good rate of fire. Also at the normal combat ranges in air to air in ww2 the range was good enough


> Hence they only used it on night fighter= short range... my point thanks



At least you agree that it wasn't because the USN wanted the 20mm for long range. By the way, where was your evidence for that claim I never did get it, or was it because you never had any evidence in the first place, so why did you make the claim?

PS they needed the 20mm on night fighters so they could get a one pass kill. All night fighters were heavily armed for the same reason


----------



## zjtins (Apr 11, 2013)

> Yes, as it proves that the 0.5 had to hit a critical area were as the 20mm didn't. Something you do not deny


but a film with many plane shot down by .50 call does not?????


How many spits were shot down in the same area? other wise the critical ares is meaningless.

Actually if he got home it was a fine, as pilots were the limiting factor not planes.


----------



## zjtins (Apr 11, 2013)

> For the USN it was a priority during the war


who cares? they did not arm their fighter with 20mm till korea.


----------



## zjtins (Apr 11, 2013)

> Being keen is wanting a better combat result because you need a better combat result.


Shooting down the enemy proves all, the .50 cal did, being keen did nothing.


----------



## zjtins (Apr 11, 2013)

> The point is simple the 30mm mk 108 had a very good ROF, it did have a slower shell with less range but it had a good rate of fire. Also at the normal combat ranges in air to air in ww2 the range was good enough


except RALL did not think so nor do the statistics prove it out (from various sources, prove me wrong)
for heavy bomber losses
ME-163 9-16 claimed 
ME-262 500 claimed 
on d-day the Germans had around 400 fighters on the western front.
The first use off the MK108 was in Sept 1943 on a ME110-G2 
Could not find the data but by the time any twin engine model were built in sufficient numbers the fighter coverage for the US destroyed them before they had a chance.

Also could not find the data: around 2500 fighter aircraft (minus me262) were used on the western front between d-day the end. Claims were around 2500 heavy bombers. Around 600 mk108 conversions appear to have been made (that is a tough number to come up with, if anyone has a better number please be my guest). 

So roughly a MK108 and non Mk108 had about the same success.

3 notes, the mk108 came out (in numbers) when air superiority was way lost. The largest use of the mk108 (me262) had a major speed advantage to all other MK-108 platforms (prop, I discounted the me-163 due to low numbers) , around 1200 me262 built only ~400 flew due to lack of fuel or engines 

so roughly speaking the fighter with MK108 had the same kill rate as those without. And the fighters with


----------



## Shortround6 (Apr 11, 2013)

zjtins said:


> who cares? they did not arm their fighter with 20mm till korea.



False.


----------



## Matt308 (Apr 11, 2013)

Hey guys I'm seeing that some snarky comments are popping up. Please keep it civil.


----------



## zjtins (Apr 11, 2013)

> Yes, as it proves that the 0.5 had to hit a critical area whereas the 20mm didn't. Something you do not deny


Exactly that's why 6x in the wings were generally needed in the case of the P-47 eight preferred. But this is not a round discussion but a plane armament discussion. More guns more rounds. Hence a a preference for 4 x20mm not 2.


----------



## Njaco (Apr 11, 2013)

In addition to what Matt stated, keep your comments to one post. These multiple posts are spam and trashing the thread. It actually helps with a better comment if you have to take the time to complete one post.


----------



## parsifal (Apr 14, 2013)

The reliability issue does raise a question for me that I know virtually nothing about. How did the 20mm, in its most common guises (Brit, Russian, German Japanese and US) compare in terms of relaiability (resistance to jams) to the 50 cal. We used 50 cals on the back of our patrol vessels, and their relaiability was legendary. They never gave us problems. How did they compare to the various types of 20mm weapon? why was the US early attempts at a 20mm weapon given such a poor report as to relaiability. was it htat bad, or were the Americans simply too entrenched at the time in their belief in the M2.


----------



## Shortround6 (Apr 14, 2013)

It has been gone over many times. 

Basically the .50 Browning was more reliable than the either the Hispano or Oerlikon guns. One question is how many or what rate of stoppage is acceptable. one stoppage per gun every 3-5 flights on which the ammo bins are totally emptied or do you NEED 5-7 flights or????

The Americans screwed up in two ways. 
1. They classified the 20mm as a cannon and not as a small arm or machine-gun. In US ordnance terms this meant that there was a bigger + / - tolerance allowed on the parts than would be allowed on a Machine gun's parts. This took quite a while to sort out.
2. They were working from original French drawings. The chamber was a bit longer than it should have been and this lead to light primer strikes. The British had already shortened the the chamber and got much better reliability but for some reason the US Ordnance dept refused to listen.
US 20mm ammunition manufacturers were not happy as production batches of ammo would fail in US guns and yet work fine in a British gun. 

There is also the question of greased or wax coated ammunition. 

See: Modifications and Attempts at Standardization


----------



## Jabberwocky (Apr 14, 2013)

parsifal said:


> The reliability issue does raise a question for me that I know virtually nothing about. How did the 20mm, in its most common guises (Brit, Russian, German Japanese and US) compare in terms of relaiability (resistance to jams) to the 50 cal. We used 50 cals on the back of our patrol vessels, and their relaiability was legendary. They never gave us problems. How did they compare to the various types of 20mm weapon? why was the US early attempts at a 20mm weapon given such a poor report as to relaiability. was it htat bad, or were the Americans simply too entrenched at the time in their belief in the M2.


 
I've found a couple of pieces of information on stoppage rates for the M2 and Hispano

In US service (Based on 8th AF over first 8 months of 1944)

Hispano: 1 per 505 rounds (P-38 only)
M2 Browning: 1 per 1442 rounds (P-51, P-38, P-47)

In the MTO:
M2 Browning: 1 per 1300 rounds in 1942, 1 per 1700 rounds (P-40s in Tunisia, not period given)

In RAF service: 

Hispano: 1 per 1500 rounds

D-Day to end of hostilities:

Hispano: 1 per 1560 rounds
M2 Browning: 1 per 3300 rounds

In RAAF service:

Hispano: 1 per 240 rounds (over Darwin, Spitfire Mk Vc with incorrely manufactured gun heating systems and) improving to 1 per 400-500 rounds later in conflict
1 per 1545 rounds (Spitfire VIII);

In RNZAF service:

1 per 600-750 rounds (Beaufighters, drum feed)


----------



## parsifal (Apr 15, 2013)

Thats very interesting. There is a bit of spread for the 20mm but for the RAF and cW, when installed correctly (ie, Darwin Wing excepted), there isnt a lot of difference in reliability.

I always believe that the 20mm was a weapon with much greater firepower that the 12.7mm weapon. I believed there was a reliability issue for the 20mm, but on the basis of that information, it does not appear to be the case. 

And no, Im not going to say "prove it". I believe you guys


----------



## nincomp (Apr 15, 2013)

Parsifal,
Your impression of the 20mm being less reliable in WWII service with the USA is not wrong. On the other hand, the British had better luck with it. 
There is an article on this subject on Anthony Williams "Cannon, Machine Guns, and Ammunition" site that discusses the 20mm aircraft gun in US service:
The Hispano-Suiza HS.404 20 mm Aircraft Gun in US Service

There are articles on WWII fighter armament as well as William's discussion of the "ideal WWII fighter armament" on this site. These articles have been brought up on this forum before, but the website is well worth a visit. 
CANNON, MACHINE GUNS AND AMMUNITION

I hope that those links work (they sure look screwy on my screen).


----------



## nincomp (Apr 19, 2013)

Earlier in this thread, someone asked how many .50 caliber bullet hits it took to bring down an opposing aircraft. 
Looking at this gun-camera footage (posted by Janisch in another thread), it appears the answer may be "sometimes, quite a few hits were needed."


_View: https://www.youtube.com/watch?v=La3qJ4sptuE_


----------



## zjtins (Apr 29, 2013)

Sorry but quite a few its not quantified nor does it tell the whole story. 

In the BoB the Brits used 1/2 to full ammo load to drop 1 German fighter. It worked by they were not happy. 

Against Japan the US (once tactics were created to fight the superior maneuverability), less than 1/2 second burst on target brought down Japanese fighters (typically), I posted a youtube video earlier showing this. 

Also you posted a video one with many off angle shots meaning many shots flat out missed, you can see the same for the German 20mm fighters having the same problem with off angle, the 20mm offered no aiming advantage. 

If you count actual hits into the engine, pilot, or fuel tank the plane shows obvious damage or is killed. 
Same goes for 20mm but it also can cause skin damage much faster which can affect airflow and reduce performance to where a second shot becomes a real probability but I argue a reduced likelihood for engine or armor penetration




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

Take a look a the infamous B-17 attack by a Bf-110 G-2. Be careful it says BF-110 G2 but the field kit could be 2x20mm and 2x30mm not 4x8mm.

Lots of misses and at the end both ball turret and rear gunner appear dead but the 4 engines are rotating.


----------



## CobberKane (Apr 29, 2013)

nincomp said:


> Earlier in this thread, someone asked how many .50 caliber bullet hits it took to bring down an opposing aircraft.
> 
> _View: https://www.youtube.com/watch?v=La3qJ4sptuE_



I've often wondered about this. The only study I know of concerning the effectiveness of armament was the By the Germans, who examined the wreckage of downed B-17s and concluded that on average it took twenty 20mm hits to bring one down. They concluded that only two percent of rounds fired in the air actually hit a bomber, ergo the average pilot would have to fire 1000 rounds of 20mm ammo to bring down a bomber - more than the ammo load of any LW single engine fighter.This information was part of the impetus towards the 30mm cannon, which required on average three hits to do the job.
The USN considered one 20mm to be equal to three .50s. The previously mentioned blog calculates 3.3 .50s. Going with the USN figure, that means it would take about 60 .50 hits to down a heavy bomber, which seems reasonable. That would require the expenditure of 3000 rounds, again more than the ammo load of any WWII fighter.
When used against fighters, I've heard the figures of 10-15 .50 hits to bring down an enemy aircraft, which should be about equivalent to 3 - 5 cannon hits. Using the same accuracy figures that the LW arrived at vs heavy bombers (a stretch, but I don't have anything else) that would require the expenditure of 500-750 rounds of .50, which would be about seven to ten seconds of fire for a fighter with six guns, which again sounds reasonable to me.
I realise I'm making pretty casual use of the data here. I'm happy with the three to one ratio for HMGs to 20mm, coming as it does from the USN and likewise the figures provided by the LW. Extrapolating from bomber intercept to fighte engagements is pushing things, but having said that the results seem pretty consistent with what I've read in combat reports and the like. If anyone has more hard data on what was required to knock down a fighter I'd love to hear it.


----------



## drgondog (Apr 29, 2013)

Shortround6 said:


> It has been gone over many times.
> 
> Basically the .50 Browning was more reliable than the either the Hispano or Oerlikon guns. One question is how many or what rate of stoppage is acceptable. one stoppage per gun every 3-5 flights on which the ammo bins are totally emptied or do you NEED 5-7 flights or????
> 
> ...



Educate me on this?


----------



## Shortround6 (Apr 29, 2013)

I believe the the Chamber was about 1mm too long, Which on case of this size is enough to screw up functioning but not enough to be dangerous. 

If you have ever seen what a .303 case looks like before it it fired in _some_ guns and what it looks like when it comes out you would see their is quite a bit of "extra" room in a .303 chamber 

Since it headspaces on the rim there is no problem with the firing pin pushing the cartridge forward.

With the rimless cartridge, you are correct, it _should_ have depended on the shoulder of the cartridge case hitting the shoulder of the chamber to position the case for the firing pin hit. But you do need a bit of tolerance. I have seen M-1s and M-14s where somebody got a little to aggressive with the reloading die show the same sort of behavior and it is why the armorers had headspace gauges, go, no go and field. The danger of case rupture is present but is rare unless head space gets way out of wack with brass OF GOOD QUALITY. Poor brass (brittle) will not stretch much before cracking. 
Some guns will fire a fair amount of the time with the extractor holding the case against the bolt face but this is not how they are designed and a "fair amount of the time" gets used up pretty quick in a machine gun (one failure in a hundred rounds?).

During WW II there were three grades of .30 cal ammo. 1st was aircraft machine gun grade, 2nd was ground machine gun grade and 3rd was rifle. The grading was done by brass quality and dimensions for functioning, not accuracy. Rifles got the "junk" as it was the least critical use. Aircraft machine guns being hard to "un-jam" in flight and a ground machine gun that jammed took out a bigger proportion of the ground units fire power than a jammed rifle. 

The 1mm too long chamber was just enough to screw up the reliability without be too dangerous. If you had the long chamber AND a manufacturing 'lot' of poor brass (either material or heat treat/anneal) you could wind up with split shoulders. 

The firing pin is pushing the entire cartridge forward in the chamber until it hits the shoulder and this cushions the blow to the primer. Not all primers had the same sensitivity. 

I hope this helps.


----------



## Jabberwocky (Apr 29, 2013)

zjtins said:


> Sorry but quite a few its not quantified nor does it tell the whole story.
> 
> In the BoB the Brits used 1/2 to full ammo load to drop 1 German fighter.



You've got proof of this, I assume. Written, video or visual?

Archie McKeller would be surprised, given that he managed to down four Bf-109s in a single flight. He also claimed three He-111s on one flight, and three He-111s and a Bf-109 on another.

Yes against German bombers, once they were armoured and had self sealing fuel tanks, the .303 generally proved inaequate. There are stories of 3 or more fighters dumping entire ammunition loads of .303 into He-111s and having the aircraft remain in the air. Of course, how many rounds were hitting will never be clear.

Against fighters, even armoured fighters, not so much. A solid burst of 1-2 seconds was generally enough to bring them down, provided the pilot hit his target.



> Against Japan the US (once tactics were created to fight the superior maneuverability), less than 1/2 second burst on target brought down Japanese fighters (typically), I posted a youtube video earlier showing this.



So you're comparing unarmoured Japanese fighters, of generally light construction and without self-sealing fuel tanks against German fighters with armour and self-sealing tanks, as your 'evidence'?


----------



## tyrodtom (Apr 29, 2013)

zjtins said:


> Sorry but quite a few its not quantified nor does it tell the whole story.
> 
> In the BoB the Brits used 1/2 to full ammo load to drop 1 German fighter. It worked by they were not happy.
> 
> ...



How can you judge how long the burst of fire is from a gun camera film ?

They're silent, plus you have no ideal if you're seeing the whole fight sequence, and some are in slow motion.
If there's gun firing sounds in the videos, it was dubbed in late.


----------



## buffnut453 (Apr 29, 2013)

I was under the impression that most gun camera installations were configured to operate the camera when the gun trigger activated so the film only captures periods when the guns were being fired.


----------



## Greyman (Apr 30, 2013)

Early war British gun cameras only exposed when the guns were fired. Later there was a delay after the guns were fired so that the effects could actually be viewed. This seems to be how American and German gun cameras operated as well. 

Generally aircraft with gun cameras also had a separate control with which to use the camera only, without the guns.


----------



## zjtins (Apr 30, 2013)

> Generally aircraft with gun cameras also had a separate control with which to use the camera only, without the guns.


True not sure when and who all did this but remember camera footage was also used for intelligence of new types not just to confirm kills.


----------



## zjtins (Apr 30, 2013)

I am using the gun camera footage plus the books I have read discussing the actual shoot downs. Not all but from what I have read for a US fighter if on target, 1/2 second has been described as all that 's needed (for a fighter). I am sure it the same for 20mm 4x guns. But having read accounts of the BoB with 8x .303, they generally describe as hosing it down until fire or loss of control occurs. Again this seems to match the gun camera footage from that era. I cannot find a definitive analysis by anyone, only test plates and estimates. So again if someone has a reference would love to see it. 

Also note few accounts of either BF109E or Spit II, V with multiple shoot downs yet the US and FW-190 have far more documented. Again rates are hard to come by but between the gun camera footage and pilot commontary seems about right.


----------



## zjtins (Apr 30, 2013)

> So you're comparing unarmoured Japanese fighters, of generally light construction and without self-sealing fuel tanks against German fighters with armour and self-sealing tanks, as your 'evidence'?


But they compare a large portion of US combat. To ignore them is to say it did not happen.


----------



## zjtins (Apr 30, 2013)

> How can you judge how long the burst of fire is from a gun camera film ?
> 
> They're silent, plus you have no ideal if you're seeing the whole fight sequence, and some are in slow motion.
> If there's gun firing sounds in the videos, it was dubbed in late.



Throw out the footage of dubious length and you are still left with clear start end sequences. Knowing they use some fraction of tracers you can count them for length of time.


----------



## zjtins (Apr 30, 2013)

> They concluded that only two percent of rounds fired in the air actually hit a bomber, ergo the average pilot would have to fire 1000 rounds of 20mm ammo to bring down a bomber - more than the ammo load of any LW single engine fighter.This information was part of the impetus towards the 30mm cannon, which required on average three hits to do the job.
> The USN considered one 20mm to be equal to three .50s. The previously mentioned blog calculates 3.3 .50s. Going with the USN figure, that means it would take about 60 .50 hits to down a heavy bomber, which seems reasonable. That would require the expenditure of 3000 rounds, again more than the ammo load of any WWII fighter.
> When used against fighters, I've heard the figures of 10-15 .50 hits to bring down an enemy aircraft, which should be about equivalent to 3 - 5 cannon hits. Using the same accuracy figures that the LW arrived at vs heavy bombers (a stretch, but I don't have anything else) that would require the expenditure of 500-750 rounds of .50, which would be about seven to ten seconds of fire for a fighter with six guns, which again sounds reasonable to me.



IMHO you are extrapolating which can lead to mistakes. 
The ME-109 did not carry 1000 rounds of 20mm even without board guns the FW-190 barely. Yet B-17 were shot down and some Germans shot down more that 1 B-17 in a fight (ever after war records showed this).

I suggest this was because novice pilots missed and good pilots did not miss so much. So the average 2% hit rate is to me very misleading. Some of the German videos show many rounds hitting. 

To extrapolate to a .50 cal round on equal terms I believe leads to a false conclusion. The variables are not sufficiently related to make that comparison.


----------



## Shortround6 (Apr 30, 2013)

You may also have to take into account ammunition used. The British tended not to mix belts of machine gun ammo but instead loaded different guns with different ammo on fighters, a common load out in The BoB was 3 guns loaded with ball (lead core) , 2 guns with AP (hardened steel core), two guns with MK IV incendiary/tracer and one gun loaded with MK VI Incendiary ( De Wilde). Later in the war Spitfires and Mosquitoes had 2 guns loaded with AP and two guns loaded with the MK VI incendiary. The MK IV incendiary was about twice as effective in setting fuel tanks on fire as the MK IV incendiary/tracer.

In many cases during the BoB the guns were set to converge too far away and the pilots were firing from waaay to far away leading to a lot fewer hits per 100 or 1000 rounds fired. British doctrine also called for a deliberate miss-alignment of the guns at times in order to give a better chance of scoring _SOME_ hits but it means that it was a lot harder to get all eight guns hitting at the same time. 

The other problem is keeping the guns on target for even 1/2 second. at 300mph the target will move 220 ft in 1/2 second and the firing plane, if doing 300mph, will also cover 220ft in the 1/2 second. The bullet "stream" may go on and off the target several times even in just 1/2 a second. From other angles and for othr targets the bulet stream may stay on the target for much more than 1/2 second. 

I am not trying to say the eight .303 gun armament was all that was needed, it wasn't, but unless you know some of the other factors going on at the times the gun camera footage was taken it is hard to evaluate the gun camera footage on it's own.

US .50 cal guns changed ammo types and ammo mixes in the belts as the war went on so trying to compare gun camera footage from 1942 to 1944 should take that into account.


----------



## Jabberwocky (Apr 30, 2013)

zjtins said:


> But they compare a large portion of US combat. To ignore them is to say it did not happen.



That's not what you were doing though. 

You were specifically comparing the firing times of .303 armament in the Battle of Britain - firing on armoured German fighters with self sealing tanks - against the .50 cal armament firing on unarmoured Japanese fighters without self sealing tanks. And, you were doing it with your own questionable estimations of "1/2 to full ammo load to drop 1 German fighter" and "less than 1/2 second burst on target brought down Japanese fighters (typically)"

Yet, you admit that you've nothing to go on but youtube videos of gun camera footage highlights, which neither know the speed of or which aircraft were doing the firing.

Do some more research (like, the US national records office and the UK national archives) before making hard conclusions.


----------



## CobberKane (Apr 30, 2013)

zjtins said:


> IMHO you are extrapolating which can lead to mistakes.
> The ME-109 did not carry 1000 rounds of 20mm even without board guns the FW-190 barely. Yet B-17 were shot down and some Germans shot down more that 1 B-17 in a fight (ever after war records showed this).
> 
> I suggest this was because novice pilots missed and good pilots did not miss so much. So the average 2% hit rate is to me very misleading. Some of the German videos show many rounds hitting.
> ...


 
The two percent figure the LW came up with was arrived at by examining downed bombers and gun camera footage - all of it, not the juicy tidbits we get off the net today. They assumedly would have looked at both the footage from experienced pilots, who as you say undoubtedly scored much higher hit rates, to novices who may have blazed away without hitting anything at all. Their intention was to determine the percentage of rounds fired by their fighter force as a body, not specifically the hit rates of experts or novices, because they wanted to reach conclusions about how the average pilot performed and whether he had the armament to do the job. Adolf Galland the actual pilot may not have needed more guns than his Bf 109 had to reliably knock down a B-17 but Johan Schmitz, the statistically constructed average pilot, did, and he was the guy you needed to cater for.
German pilots did shoot down multiple B-17s, which suggests to me one of two things: either they were experts who were scoring considerably more hits than the average pilot could expect too, or (less likely but it undoubtedly occurred) they were less than expert pilots who got lucky.
I agree that I am largely speculating with my figures for the .50, although I am at least extrapolating from the basis of the LW study and the USN standard that one 20mm equals three .50 in firepower. I don't recall where I got the figure of 10-15 hitsbeing typically sufficient to down a single engine fighter (and it may have been referring to the PTO) but the 7-10 seconds of fire seems about right, for what that's worth.
So, as I said I'd love to see some direct studies of the effects of .50 cal fire, but lacking that all I can do is work with the USN and LW stuff. Not perfect, but then again some people maintain that HMGs alone should have been fine for tackling heavy bombers and the like, and I've never seen ANY evidence for that.


----------



## Greyman (Apr 30, 2013)

CobberKane said:


> I agree that I am largely speculating with my figures for the .50



You are exceedingly close to the actual figure at which the British arrived (for a Heinkel 111). When I get a few minutes tonight I'll try and relay the figures.

EDIT:

Alright, basically it broke down to this:

25% chance of Lethality
20 mm HE/I - 4 rounds
.5 inch AP - 11 rounds
.303 inch - 24 rounds

50% chance of Lethality
20 mm HE/I - 9 rounds
.5 inch AP - 20 rounds
.303 inch - 42 rounds

75% chance of Lethality
20 mm HE/I - 17 rounds
.5 inch AP - 33 rounds
.303 inch - 67 rounds

90% chance of Lethality
20 mm HE/I - 29 rounds
.5 inch AP - 50 rounds
.303 inch - 105 rounds

The tests were based on ground-firing trials against a Heinkel III, 200 yards direct astern and assumed a uniform distribution of strikes over the airframe.

The British analysts remarked that the figures were probably slightly pessimistic due to the impossibility to simulate airframe disintegration (lack of air stresses) and it was not possible to assess on a statistical basis the myriad of ways a fire could start due to engine behavior under fire.

During the test they didn't have proper stats on the likelihood an HE/I round would set a petrol tank on fire. Based on four strikes, the tank lit up once, so they went with 25%.
Afterwards they were able to do more extensive tests and found this was 40% (this time based on 60 strikes). This was indicated in an addendum to the firing trial.

Also, fuel leaks were not factored in. The thinking was that German bombers operate from such short distances to their targets, the chance of petrol tanks being holed and emptied was removed. I would think this would hurt the Hispano numbers more than the two Brownings.


Your 'two percent' hit accuracy figure sounds reasonable to me as well, as the figure I think I've generally run into is about one percent accuracy. If you were isolating the statistic against large bombers that weren't maneouvreing, a doubling of hits would seem to fit.


----------



## zjtins (May 1, 2013)

> Yet, you admit that you've nothing to go on but youtube videos of gun camera footage highlights, which neither know the speed of or which aircraft were doing the firing.


Not sure how you can conclude that when I specifically talked about books from pilots from WWII and compared the results as being similar. 

I tried several national archives but several have been turned off after 911 you have to have a clearance now. If you know of one that is still open I will research it. 


Greyman now that is interesting data, I assume lethality as likelihood of bomber going down. 

But it shows the ratio for number of 50.cal to 20mm rounds reducing for a greater liklehood of shootdown.
25% 2.8
50% 2.2
75% 1.9
90% 1.7


Assuming the ROF for the .50 and 20mm were close then

2x20mm 4x20mm setup vs 6 and 8 gun .50cal setup @50% lethality

2x20mm 0.7 and 0.6 of 6 and 8 gun
4x20mm 1.5 and 1.1 of 6 and 8 gun

So a 2 x20mm is worse than a 6 or 8 gun .50 but 4x20mm is better.

But to give an idea of other factors influence, when the Germans went to the gyro sight they claimed a 30% increase in hit probability. 
30% is around the delta between the 2x20mm and 6 gun .50 and more than the delta between the 4x20mm and 8 gun .50 cal setup.

Also the longer the shooting the less the difference to bring the Heinkel down. Granted we don't know the wind/loading affects and the 20mm has an advantage there but unless its is major impact then its just another complicating factor.


----------



## RCAFson (May 1, 2013)

Greyman said:


> 90% chance of Lethality
> 20 mm HE/I - 29 rounds
> .5 inch AP - 50 rounds
> .303 inch - 105 rounds
> ...



The effectiveness of the .303 is interesting; if we assume 14rps for the .5in and 20rps for the .303, it would seem that 8 x .303 is roughly equal to 6 x .5in, yet the 8 x .303 battery is much lighter, ditto for 4 x 20mm cannon at 10rps.


----------



## zjtins (May 1, 2013)

> The effectiveness of the .303 is interesting; if we assume 14rps for the .5in and 20rps for the .303, it would seem that 8 x .303 is roughly equal to 6 x .5in, yet the 8 x .303 battery is much lighter, ditto for 4 x 20mm cannon at 10rps.


Now you get it!

The P-47 was big and had a huge engine and could lug 8x50cal. The rest of the AF/Navy (generally) had 6x.50 and had engines big enough to lug them around. 
The Spit was too sluggish with 4x20mm as was the ME-109 with more than the 1x20mm and 2 MG. 

There were all kind of tradeoffs each country/AF had to make for their situation. They had constraints they just could not build what every they wanted, plus political infighting, plus not having hard data. All sides were way off in both actual kills and enemy estimates. How does one select a weapon/weapon system or setup when the input so cloudy? 
BTW the Typhoon (?) I think was the fighter had 12X.303 until they got some 20mm available. I could not find any record of combat with it.

However the range the .303 in terms of bullet momentum dropped off much faster than the .50 cal AP so range would be a bigger factor in combat that was not measured. 

I can prove it but that seems to be a big problem in the BoB as it appear that many novice pilots opened up at too great a distance, losing momentum, surprise and not a the optimum distance for the gun angles.


----------



## Greyman (May 1, 2013)

A couple more things I forgot to add about the test, things that would hurt the 20-mm numbers more than the others'.

During the test they didn't have proper stats on the likelihood an HE/I round would set a petrol tank on fire. Based on four strikes, the tank lit up once, so they went with 25%.
Afterwards they were able to do more extensive tests and found this was 40% (this time based on 60 strikes).

Also, fuel leaks were not factored in. The thinking was that German bombers operate from such short distances to their targets, the chance of petrol tanks being holed and emptied was removed. I would think this would hurt the Hispano numbers more than the two Brownings.

I'll edit the original post and add this info as well.


----------



## CobberKane (May 1, 2013)

zjtins said:


> Not sure how you can conclude that when I specifically talked about books from pilots from WWII and compared the results as being similar.
> 
> I tried several national archives but several have been turned off after 911 you have to have a clearance now. If you know of one that is still open I will research it.
> 
> ...



On the whole the info would seem to be compatible with the LW and USN conclusions. The LW were looking at the average number of 20mm hits required to bring down a bomber, so their conclusion of twenty hits would correspond to the British findings for 50 percent lethality. The Brits found it took nine hits to achieve 50 percent lethality on an He 111, the Germans concluded that it took twenty hits to achieve the same on a B-17, which would make the four engine bomber a little more than twice as tough as the twin. Halve it again and you get 4-5 (12-15 .50 cal) hits fot a fighter, again in the ballpark.
As you point out, at 50 percent lethality it takes 2.2 .50 rounds to do the work of one 20mm, so the USN idea of one 20mm cannon being equal to about three .50 cals is also supportable, particularly given the factors Greyman mentioned that may has penalised the 20mm somewhat.
What isn't considered here is the lethality of the weapons in proportion to weight. I haven't done the sums but I'm betting that one 20mm with ten seconds of ammo would weigh quite a bit less than the equivalent three .50 cals with the same firing time (or even a bit less ammo if the .50s higher ROF would allow it to score the required number of hits in less time). If that's so, to my mind the 20mm is clearly the better weapon once the battle is joined, but this does not invalidate the US decision to stick with the .50 given its demonstrated effectiveness in the use to which it was being put, logistical considerations etc.


----------



## Jabberwocky (May 1, 2013)

Greyman said:


> You are exceedingly close to the actual figure at which the British arrived (for a Heinkel 111). When I get a few minutes tonight I'll try and relay the figures.
> 
> EDIT:
> 
> ...


 
Taking a theoretical on-target burst with a 90% chance of leathality, for the following set up's you'd need the following firing times

2 x Hispano II (~650 rpm): 1.33 seconds
2 x Hispano V (~750 rpm): 1.16 seconds
4 x Hispano V (~750 rpm): 0.58 seconds
6 x M2 (~800 rpm): 1.25 seconds
8 x M2 (~800 rpm): .94 seconds
4 x .303 Browning (~1150 rpm) 1.36 seconds
8 x .303 Browning (~1150 rpm): 0.68 seconds
12 x .303 Browning (~1150 rpm): 0.45 seconds

That makes the .303 appear obscenely good. And also the mixed .303/20 mm battery. Unfortuantely, it doesn't include things like dissimilar ballistics and gun positioning.


----------



## Shortround6 (May 1, 2013)

It also doesn't take into account different ammo types.

British were using 4 different types of projectiles in the .303 during the Bob. 

The Americans had .50 cal ball, AP, tracer and incendiary up until 1943 when they began to introduce the M-8 API. By some point in 1944 most fighters were using almost 100% M-8 API. M 23 incendiary was coming in at the end of the war I believe? 

Not only do the Hispano rounds vary but even on the same type shell (HE) the fuses were changed at times. 

The trial results are a nice find but they represent a snapshot in time of the weapons capability at the time of the trial/test.


----------



## CobberKane (May 1, 2013)

I'd suggest the .303s might be getting a break because the test was conducted at comparatively short range (200 yards.) The destructive power of the 303 rounds could be expected to drop off more rapidly than that of the .50 or 20mm. As aircraft speed increased throughput the war so did typical ranges, which would have further worked against the 303. This might account for the apparent effectiveness of the 303 in this test compared to the combat experience of pilots, who generally considered it inadequate as sole armament.


----------



## Glider (May 2, 2013)

On the Williams web site it gives the time taken to match the firepower of the Me 262 for one second.

For the 
6 x 0,5 it takes 6.5 seconds
8 x 0.5 - 4.8 seconds
8 x LMG - 14.5 seconds
4 x 20mm Hispano II 2.9 seconds
4 x 20mm Hispano V 2.3 seconds
Jap 4 x type 99-2 4.8 seconds

It seems to be broadly inline with the above comments. What is interesting is that he allows for the effect of Sync on the aircraft when comparing aircraft with different weapons. So a 

190 A8 takes 2.8 seconds
La 7 - 7 seconds
Spit 2 x 20mm and 4 x LMG - 4.8 seconds
Spit 2 x 20mm and 2 x HMG - 4.5 seconds
109 F 1 x 20mm and 2 x LMG - 10.3 seconds
P38 5.3 seconds 

It does show how the 20mm made a significant difference to the firepower of the aircraft. Also that USAAf fighters had at best average firepower for the war in 1944/5 but that was sufficient for the targets they were shooting at


----------



## Jabberwocky (May 2, 2013)

CobberKane said:


> I'd suggest the .303s might be getting a break because the test was conducted at comparatively short range (200 yards.) The destructive power of the 303 rounds could be expected to drop off more rapidly than that of the .50 or 20mm. As aircraft speed increased throughput the war so did typical ranges, which would have further worked against the 303. This might account for the apparent effectiveness of the 303 in this test compared to the combat experience of pilots, who generally considered it inadequate as sole armament.



I think you're onto the right path.

The tests and analysis I've seen suggests that the 12.7 x 99 round was somewhere between 1.9 times and 4.1 times as effective as a light machine gun round like the .30, .303, 7.92, 7.62 Soviet.

Most LMGs were probably only about 1/4th to 1/3rd as effective as the big Browning, but some guns made up the difference with very high RoFs. The US and UK Browning had RoFs of about 1150-1350 rpm, the MAC 1934 had a RoF of about 1400-1500 rpm and the ShKAS had a RoF of about 1800 rpm.

Where the LMGs also make up ground on the Browning is their weight (ranging from 7.5 kg to around 12 kg, compared to the M2's weight of about 29 kg). This means that while the M2 was very *effective*, it wasn't very *efficient*.

Thinking about it, I believe that's where a lot of the argument about the M2 vs the 20 mm is coming from.

The M2 Browning was a big, heavy weapon, firing a big heavy round at a high velocity at a reasonable rate of fire. That means that while in terms of damage to targets, it was effective, it was also not very efficient. Lots of firepower, not that much efficiency.

The Hispano was also a big heavy weapon, firing a big heavy round at a high velocity at a moderate rate of fire. However, in terms of firepower per weapon, it was much more efficient that the M2. More firepower, but also more efficency.


In terms of gun efficency, the M2 is about middle to bottom third when it comes comparing WW2 aircraft basic gun 'efficency' measures like muzzle energy vs installed gun weight, or throw weight vs gun weight or ammunition power vs gun weight.

That means that while both the M2 and the Hispano were effective at destroying targets, the M2 was less efficient, in the fact that US fighters had to carry around heavier batteries of weapons and larger amounts of ammunition that their contempories mounting cannon. 

The installed weight of an M2 Browning and ancillaries was between about 70 and 75 lbs.
With 6 .50 cals and 275 rpg, total installed armament weight is about 830-860 lbs
With 8 .50 cals and 275 rpg, total installed armament weight is about 1105-1145 lbs

The installed weight of a Hispano II was about 147 lbs (and about 132 lbs for a Mk V)
With two cannon and 120 rpg, total installed armament weight is about 444 lbs.
With four cannon and 120 rpg, total installed armament weight is about 888 lbs.

If you agree that 1 Hispano was equal in firepower to somewhere around 2.5 to 3.5 M2s (and I do), then you could give all US fighters 2 x 20 mm Mk II with 120 rounds each (11-12 seconds firing time) and 2 x .50 cal with 275 rounds (20-21 seconds firing time) for about 585 lbs, installed weight.

This gives you roughly the same firepower as a P-47 for half the installed weight of its eight M2s or 70% of the installed weight of six .50 cals. So, you save somewhere around 520-550 lbs on a P-47, or 245-275 lbs on a six gun US fighter. 

How much acceleration, rate of climb, rate of turn is that kind of weight shedding worth to a pilot in combat?

When they re-designed the P-51 to make the H model, the goal was to shave 600 lbs off the design. If the USAAF had armed it with two of the later Hispano Mk Vs and two M2s, then they'd have had a head start of nearly 275 lbs.


----------



## GregP (May 2, 2013)

Regarding post #125, ins't that a YB-40?

Seems to have two turets on the belly.


----------



## zjtins (May 2, 2013)

A P-47 with 8x.50 or 6x.50 Mustang was more efficient than a BF-109 with 1x20mm and 2 MG.


----------



## zjtins (May 2, 2013)

> I'd suggest the .303s might be getting a break because the test was conducted at comparatively short range (200 yards.) The destructive power of the 303 rounds could be expected to drop off more rapidly than that of the .50 or 20mm. As aircraft speed increased throughput the war so did typical ranges, which would have further worked against the 303. This might account for the apparent effectiveness of the 303 in this test compared to the combat experience of pilots, who generally considered it inadequate as sole armament.


I concur and that is one of the problems with test results combat results.

Extreme case is Germans wanting a 50mm or 75 mm round to take out a bomber in theory 1 round= 1 bomber much of the time. But the drawbacks for the implementation was not overcome in time. 
That is my issue with the 20mm vs 50cal only looking at the round(s) and not the system.


----------



## Shortround6 (May 2, 2013)

zjtins said:


> A P-47 with 8x.50 or 6x.50 Mustang was more efficient than a BF-109 with 1x20mm and 2 MG.



I really do have to question if English is your first language. 

Not meant as an insult but I am wondering if we have a translation problem. 

There is little or no question that "8x.50 or 6x.50" is a more _EFFECTIVE_ armament than 1x20mm and 2 MG. 

_Efficient_ brings in additional conditions or factors.


----------



## Glider (May 2, 2013)

zjtins said:


> A P-47 with 8x.50 or 6x.50 Mustang was more efficient than a BF-109 with 1x20mm and 2 MG.


But you miss something. When the 109 with 1 x20 and 2 x Hmg was fighting the P51 normally had 4 x HMG so the firepower was in the 109 favour. Later the 109 were normally armed with 1 x 30mm and 2 x HMG, again the advantage was with the 109


----------



## Jabberwocky (May 2, 2013)

zjtins said:


> A P-47 with 8x.50 or 6x.50 Mustang was more efficient than a BF-109 with 1x20mm and 2 MG.


 
I honestly can't tell if you're being serious.

The 1 x 20 mm and 2 x MG131 set up on the Me 109G5 onwards had about 70-80% of the firepower of the 6 M2s set up on the P-51, depending on which measure of firepower you want to use.

However, the Bf-109 has a much more efficient mounting, being centreline focused rather than spread across the wings. The mix 20mm/13.2 armament loses out a little with dissimilar ballistics, although not too much, as very few fighters were firing at targets beyond about 600m.

With 6 M2s and a total of 1880 rounds of ammunition, the P-51D's armament weight is just over 900 lbs. 

With the MG151/20 and 200 rounds and the MG131 and 300 rounds per gun, armement weight is just over 300 lbs.

So, for one third of the P-51Ds armament weight and very similar trigger time (17 seconds for the MG151/20 and 20 seconds for the MGs), you get 70-75% of the firepower. 

You could *double* the armament installation with the Bf-109 and still have less installed armament weight that the P-51D and a 40-50% advantage in firepower.


----------



## CobberKane (May 3, 2013)

Leaving aside the specifics, its interesting to note that controlled analysis of data from controlled tests and conclusions drawn from real world experience often yield different results. Purely in terms of combat the 20mm outperforms the .50 comprehensively, but once we take into account the USAAF's established supply lines and the fact that American fighters were engaged overwhelmingly against other fighters, the case for converting to cannon is weakened. On the other hand the British started out using rifle caliber MGs against bombers and, results of the test conducted at 200 meters notwithstanding, the practical experience was that these were inadequate, lending impetus to the adoption of cannon.
The Germans ultimately tended towards the 30mm cannon as their best air to air weapon, and looking at the data for relative firepower and efficiency this would seem to be a no-brainer. But the Germans were concerned with knocking down large, tough bombers flying in straight lines; the firepower/efficiency numbers take no account of the difficulties of using such a slow firing, low velocity weapon against other fighters. Thus the 30mm would have made sense to the LW, but not the USAAF. 
Purely in terms of firepower and efficiency the P-51H might have been better off equpiped with cannon or a cannon/HMG mix. But would the cannon fairings have created more drag than the extra firepower was worth, given the designers might never have envisaged their aircraft operating against tougher opposition than was already being encountered by the P-51D? And even if the short barrel 20mm as used in the Tempest V had been available, maybe the designers were already looking at the latter versions of the .50 with greatly improved ROF, as used in the Sabre.
The 303 looks surprisingly good in the tests, but aircraft were getting faster and typical ranges of engagement were increasing. Even in 1943 it must have been obvious that the next generation of fighters, and the jets to follow, would be firing on each other well beyond the ranges that the 303 would retain significant hitting power. Even the improved fifty cals of the Sabre were beginning to dull by the time of the Korean war.
The tests are interesting because they give us a basis to work from. Historically there is a general progression in primary air to air armament; from rifle caliber MGs to HMGs to cannon to guided rockets. Tactical considerations like logistics or the nature of the opposition might have delayed or influenced this progression, but at the end of the day the air forces concerned adapted what worked.


----------



## zjtins (May 3, 2013)

> But you miss something. When the 109 with 1 x20 and 2 x Hmg was fighting the P51 normally had 4 x HMG so the firepower was in the 109 favour. Later the 109 were normally armed with 1 x 30mm and 2 x HMG, again the advantage was with the 109


The P51 always had 6 not 4 MG. The Apache had 4x20mm.


Efficiency has a denominator, name your denominator so we can talk on equal terms.


----------



## zjtins (May 3, 2013)

The MG131 was underpowered vs the Browning. 
If you want pure efficiency then a.22 would look really good... but no on used it. For that matter the .30 probably look very efficient.

Efficiency is only one factor, it not effective then its moot.


----------



## Jabberwocky (May 3, 2013)

zjtins said:


> The P51 always had 6 not 4 MG.



Well, except for the 900 P-51/Mk 1s AND the 1500 P-51As AND the 3750 P-51B/C AND the 850 Mk IIIs then yes all P-51s had six M2s


----------



## zjtins (May 3, 2013)

Well, except for the 900 P-51/Mk 1s AND the 1500 P-51As AND the 3750 P-51B/C AND the 850 Mk IIIs then yes all P-51s had six M2s
And how many were in Air-Air combat.

Fine not all, most, a large number, the most popular model, 11,000 whatever you want.

Now I expect you to chastise Glider just as hard since he said they all normally had 4 MG in the first place.


----------



## zjtins (May 3, 2013)

Minus 1578 Allison powered P51's they were undoubtedly used as ground attack. So 10,116 H/K models, 3738 B/C Rolls Royce powered. A 2.70 ratio for 6 guns I do not see how that is considered normally 4 MG


----------



## Glider (May 3, 2013)

zjtins said:


> Fine not all, most, a large number, the most popular model, 11,000 whatever you want.
> 
> Now I expect you to chastise Glider just as hard since he said they all normally had 4 MG in the first place.



Jabber and I are fine. We recognise what matters isn't how many but when the aircraft were introduced. By the time the P51D came into service most of the Me109 had 1 x 30mm and 2 x HMG.

PS you do know the difference between a P51D, a P51K and a P51H don't you?


----------



## CobberKane (May 3, 2013)

zjtins said:


> The MG131 was underpowered vs the Browning.
> If you want pure efficiency then a.22 would look really good... but no on used it. For that matter the .30 probably look very efficient.
> 
> Efficiency is only one factor, it not effective then its moot.


 
Efficiency as discussed here is a function of mass AND firepower, so irrespective of the light weight of your hypothetical .22 mg, it would never be éfficient' because it's obvious lack of firepower would totally hobble it.


----------



## Njaco (May 3, 2013)

zjtins, keep your posts to one post. I don't know why that is so hard to understand.


----------



## Aozora (May 3, 2013)

zjtins said:


> Minus 1578 Allison powered P51's they were undoubtedly used as ground attack. So 10,116 H/K models, 3738 B/C Rolls Royce powered. A 2.70 ratio for 6 guns I do not see how that is considered normally 4 MG



Assuming that no Allison engine P-51s engaged in aerial combat...


----------



## CobberKane (May 4, 2013)

Aozora said:


> Assuming that no Allison engine P-51s engaged in aerial combat...



And they did, of course, in the Pacific and the ETO. According to "Clash of Wings" at least one Apache pilot became an ace.


----------



## zjtins (May 6, 2013)

> And they did, of course, in the Pacific and the ETO. According to "Clash of Wings" at least one Apache pilot became an ace.


So 4 x50 cal was good enough


----------



## Shortround6 (May 6, 2013)

Apaches had SIX .50 cal guns. Two in the fuselage and two in EACH wing.


----------



## zjtins (May 6, 2013)

> Apaches had SIX .50 cal guns. Two in the fuselage and two in EACH wing.



Ok so you are backing my arguement thanks.


----------



## Glider (May 6, 2013)

zjtins said:


> Ok so you are backing my arguement thanks.


Priceless

If you follow this logic

.


> So 4 x50 cal was good enough


 because one apache pilot made an ace then

4 x LMG in a light medium bomber is good enough, as one pilot made ace flying Marylands


----------



## zjtins (May 7, 2013)

More info Declassified in 1973 it is test data from 1952, 20mm vs new 20mm vs .50 all AP.


----------



## tomo pauk (May 7, 2013)

Thanks for the table. It shows nicely indeed how the 20mm would pierce the armor plates with 500-900 ft/sec less speed than .50.


----------



## CobberKane (May 7, 2013)

There seems to be a bit of a fan base out there for the 4x50 cal arrangement. I'd suggest that it was adequate against fighters in the ETO, going on the results of pilots flying the P-51 B and C, but the progression to 6xHMG in the D models indicates that there was a recognised need for more firepower. That said, I believe many pilots kept the extra guns in reserve and didn't use them until the inboard four had run dry anyway.
In other threads there have been opinions that 4xHMG should have been sufficient for knocking down heavy bombers, which still seems far fetched to me. But the USAAF and USN were never faced with that task, which I suspect was major factor in their retention of the .50 as the weapon of choice on their single engine fighters.


----------



## zjtins (May 8, 2013)

View attachment 232921
View attachment 232922
View attachment 232921
View attachment 232922


> Thanks for the table. It shows nicely indeed how the 20mm would pierce the armor plates with 500-900 ft/sec less speed than .50.


But that is not the whole story, look at the right column which include angles (from the second to last column). The numbers are quite even. Now take that and rate or fire for an aircraft and the numbers swing in favor of more .50s than less 20mm gun on an A/C.

Separate issue also found this from Knight of the Skies Knights of the Skies: Armour Protection for British Fighting Aeroplanes Michael C Fox, p133
of interest
1 it was done at 600 yards which later they knew was not what a fighter should strive for
2. in section V they state no point in using the .50 cal.. However nowhere does it even mention it being tested. If this were the basis of 20mm vs .50 choice they never even tested the .50 cal based on an assumption.


----------



## tomo pauk (May 8, 2013)

zjtins said:


> ...
> But that is not the whole story, look at the right column which include angles (from the second to last column). The numbers are quite even. Now take that and rate or fire for an aircraft and the numbers swing in favor of more .50s than less 20mm gun on an A/C.
> ...


Maybe you should take a long good look at the table - the angled steel plates are the 1st (1/2in face hardened plate, inclined at 30 deg) and second one (3/4in Homogeneous plate, inclined at 30 deg). The 'old' 20mm comfortably outscores (= needs much less velocity to pierce) the .50 there, as it does when hitting the 1in Homogeneous plate. 
You can also note that they did not bothered with .50 to pierce the 1-1/4 in Homogenous plate.


----------



## zjtins (May 9, 2013)

How many planes in WWII and Korea carried 1 1/4" of armor? None I know of. Most armor seems to be around 9-15mm or around the .5 inch plates. 
My point is these tests do not show the 20mm AP as 2x or 3x better than .50 cal API. Am I saying they correlates directly to planes being shot down.... no. But its does support the notion that a slower rate (or aircraft rate of fire) with what appears only a slightly more capable round is not 3x better than a greater rate (or aircraft rate) with a slightly less capable round. Again this ignores HE vs AP also but we don't seem to have data on what actually brought planes for mixed ammo types.


----------



## Shortround6 (May 9, 2013)

"slightly more capable round" ?

ROFLMAO

I guess the .50 Browning was a _slightly more capable round_ than the .30-06 too


----------



## zjtins (May 10, 2013)

Glad your are laughing
Just found ADA800394. May 1947 Airplane Vulnerability and Overall Armament Effectiveness 


Will take a while to pull the info into .png's but one figure shows: 


Compares Armament for Multiple Attack Fixed gun fighter (limited to 1000 lbs of guns and ammo 100 rounds typical) - Time required for 50% probability of a kill of a B-25 at 500 Yards.

And to take out both engines and pilots. 

time in sec for 50% probability
.50 APIT M2 3.2sec 
.50 API ME 2.2sec
20mm INC M2 1.8sec
20mm HEI M2 4.0sec
20mm INC M3 1.6sec
30mm HE MK108 0.4sec
30mm HE MK103 1.3sec
37mm HE M10 2.2sec
37mm HE M9 4.7sec
75MM 4.1 sec

not sure of what the 20mm INC means it's photocopied to PDF so I cant search. 

more to come


----------



## Juha (May 10, 2013)

My guess is that INC stands for incendiary.

Juha


----------



## altsym (May 10, 2013)

I'd have to give the edge to the 2 x MG131 + 1 x Mk108 cannon. Devastating firepower in a compact package.


_View: https://www.youtube.com/watch?v=ZoLLDi-M3fk_

Now imagine 6 x MK 108 in the nose of a Me 262 A-1a/U5.


----------



## zjtins (May 13, 2013)

From Page 18
C Supplementary Tests
Several tests now in progress and' also to be-conducted in the near .future are designed
to supplement information obtained from firings against aircraft. Such tests are concerned with the actual
mechanics of fuel tank ignition and include ignition of fuel tanks by fragments. One such test, recently
completed, involved the detonation of a 20mm high explosive incendiary round in the middle of a fully loaded
B-17 main fuel tank. *The lack of fire served to verify and emphasize the importance of ignition of-the vaporized
fuel at the surface of the tank.*
Page 19
The last two columns in Table E2 list the average "A" and "B" assessments given to
fires obtained in previously damaged cells. In each case the assessments pertain to the corresponding type
of aircraft. It is clear that the relative frequency of fuel fires and leakage is.not sufficient as a description
of fuel tank vulnerability. The severity of fires and-the location of fuel tanks are important to the overall
vulnerability of the fuel system. In general,, it appears that the higher the probability of causing a fire,
the higher the severity of fires when they do occur. The Cal. 0.50 ammunition caused no single-shot fires
which had any chance of causing the plane to crash within five minutes. Among the small calibers, only the
Cal. 0.60 displayed the ability to cause any appreciable single-shot "A" damage through fires. This may be -
due to the relatively high striking velocity for this caliber, resulting in more two-wall penetrations of fuel
cells. The 20mm rounds resulted in fires causing good "B" damage but not enough for high "A". It is expected
that this caliber will show up much better in firings against the lower surface of the wing. The higher
blast effect from the 20mm rounds results in larger holes on entry into the top of the fuel cell, but no damage
to the lower part of cell in contrast to the effect of the Cal. 0.60. *The resulting fires then are relatively
weak, not being fed by a stream of fuel. Often they are blown out.by the slip stream of air provided by the
slave engine. *In firings from the front and below, it is expected that fires caused by the 20mm rounds will
prove-much more damaging.

The 20mm INC is incendiary M96.


----------



## zjtins (May 13, 2013)

Some files.
Note had a duplicate. Added the single round Pk to the multi-round time to Kill. Due to distributions it means one cannot simply multiply individual round hit Pk to scale up to get Pk for a plane from a fighter weapon setup, its more complex. 


View attachment 233277
View attachment 233278
View attachment 233279
View attachment 233280


----------



## zjtins (May 13, 2013)

Sorry mod
Last note the F-86 used in Korea used the ANM3 version of the .50cal which had a 1200 rpm rate vs 800 rpm for the ANM2. From another AD Doc


----------

