Allied Fighter vs Fighter: Is it really necessary ???

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how stupid were the USAF for fitting 6 and even 8 x .50s to there aircraft
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The real problem is the U.S. badly botched their effort to mass produce a decent 20mm aircraft cannon. Without a reliable 20mm cannon what other choice does the USAF have except to use .50cal MGs in ever increasing numbers?
 
FASTMONGREL

The point was, the British supposedly asked for 6 guns to be placed in a moderately performing fighter, thus reducing its performance even more. Placing 6 guns in a P51, F4U or F6F, or 8 guns in a P47, much more powerful and advanced planes which arguably had a decisive advantage in performance over their rivals wouldn't have been an issue.
 
DAVEBENDER

I tend to think the .50 was a better choice against single engine fighters than the 20mm, due to being able to carry so much more ammo per weapon. Since the US didn't face large heavy bombers I tend to think the lack of a good 20mm wasn't really much of an issue. Had we faced German B17 or B 24 type aircraft, I believe it would have definately become an issue. One question, wasn't the 20mm on the P38 and P61 a reliable weapon? If so, did it have to do with the difference between it being mounted on a solid internal mount and being mounted in a flexible wing?
 

The USAAF had this to say about the mid 1943 P-38 armament:

i. The guns will not feed properly during maneuvers which create a pull of greater than 3-1/2 G's.
P-38 Performance Trials
but they don't distinguish between the .5" and the 20mm.
 

You say the Wildcat was amoderately performing fighter but renrich says it was an excellent performing fighter. So I am confused as to how an extra 2 .50 Brownings ruin performance so much when as I understand it the total ammunition capacity was roughly the same between the 4 gun plane and the 6 gun plane.
 
Air combat is largely a factor of altitude advantage and surprise. The primary purpose of a carrier borne fighter was to protect the fleet and to do this the fighter had to kill the attacking bombers. I think the FAA wanted a 6 gun Martlet/F4F because they reasoned that the average pilot was unlikely to get more than one pass at a target, therefore it made sense to optimize the firepower to maximize hit potential during each pass. There's not likely to be much difference in actual weight between a 4 gun F4F with 450 rounds/gun and a 6 gun f4F with 240 rounds/gun. The most successful FAA fighter on the Malta run appears to have been the 4 x 20mm armed Sea Hurricane IC, which supports this logic.
 
davebender said:
If that was true then modern fighter aircraft like the F-15 and F-16 would still be armed with .50cal MGs rather then a 20mm cannon.
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Cannon or Machine Gun – Evaluation
How did the British 20 mm cannon compare with the American HMG-only concept?

The first problem to be considered is that the cannon of the combating nations varied hugely in size, weight and performance. The MG FFM, Type 99-1 and B-20 were all lighter than the American 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 cannon gains most ground over the HMG. 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 at all. 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 fairly typical late-war 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.

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 heavy machine gun had had its day
 

The F4F-3 had the two stage supercharged engine and so had rather different performance above 15,000ft than the other Martlet/Wildcats.
As far as "IF the US had been on a war footing" The Problem was not only Grumman but Pratt Whitney.
One if not two Army fighters in the Army 1939 fighter competition were powered by TWO stage supercharged R-1830s. They worked so well (sarcasm) that not only did the Army buy single stage planes (P-40) but it was the final straw that saw P&W stop using General electric designed superchargers. This redesign of the superchargers took time.
While the US Navy did order F4F-3 in Aug of 1939, the French also ordered an export version using the Wright cyclone engine. This engine, while it did offer the same 1200hp for take-off was good for 1000hp at 13,500ft compared to the 1000hp at 19,000ft of the P&W R-1830 that would eventually be in the F4F-3. The French version was to be armed with six 7.5 Darne mg. They were not finished when France fell and the order was taken over by the British. The US Navy allowed this French/British order to be delivered before it's own orders. This aircraft (the Martlet I) was changed to four .50 cal guns, did not have self sealing tanks or armor and had fixed wings and no carrier equipment. They were used as land based fighters. These are the ones that show up on July, 1940. It takes until Oct 31 1940 for the 81st Martlet I to be delivered. It takes until Dec 1940 for the 22nd F4F-3 to be accepted by the Navy out of 578 on order.
Because of difficulties with the two stage engine a two speed single stage engine installation has been worked out and flown as the XF4F-6. It is ordered into limited production as the F4F-3A. This is the engine used in the Martlet II and III. It was good for 1000hp at 14,500ft.
The British got 1082 Martlet/Wildcats out of 7905 produced. considering that 111 of them were from picking up the French and Greek orders and the last 340 weren't supplied until 1944 I hardly think British requirements had much influence on the Wildcats design or development.
A number of the US F4F-3 and F4F-3A were completed without selfsealing tanks.

The XF4F-3 isn't flown until until Feb 12 1939. It needs wing and tail modifications. In May it is still suffering from persistent cooling problems but they are finally solved. Navy places first order in Aug.
Even if Grumman goes on a "WAR FOOTING" the next month just how much faster could thy have turned out any large numbers of Wildcats? It took North American about a year to deliver the first production Mustang after the prototype flew. And North American wasn't dealing with a temperamental prototype supercharger set-up. Even if everything went extremely well you would probably be lucky to get a couple of hundred F4Fs into service during the BoB without totally rewriting history.
 
davebender said:
If that was true then modern fighter aircraft like the F-15 and F-16 would still be armed with .50cal MGs rather then a 20mm cannon.
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That might be true if the enemies jet fighters grossed 6,000-8,000lbs and had fuselage-wing skinning the same thickness as WW II 350-450mph aircraft.

Since a Mig-29 weighs empty about what a Martin B-26 bomber from WW II does I think we can see that this argument is a non-starter.
 
The American Army was partially mobilized during the summer of 1940. A massive naval building program was also in progress by mid 1940 including the first two Essex class aircraft carriers. So there should have been no shortage of money for military aircraft.
 
Glider, without going back through the report, I am pretty sure that the Wildcats tested in the Jan. 41 tests at Anacostia had armor which surprised me also.

Without getting into the debate about whose guns and how many and all the ballistics and other BS which we have had here before besides which we do not have Soren and HoHun to keep us straight, it is very clear according to Lundstrom in "The First Team" that when the F4F4 was under development, the British insisted on six guns against the wishes of the USN. If one reads my post carefully I said that the F4F4's performance drop, compared to the F4F3, was partly caused by the six 50 BMGs. The other factors were the weight of the folding wings and a few other modifictions and the drag of six gun ports is more than four. Grumman had to revise the gun layout to accomodate the six guns along with the folding wings and they did not want to build two versions of the F4F4. I have a feeling that everyone went with the Brit's desires because they had been in combat since 1939 and the US had not. Having said that, the USN did not like the six guns in the Wildcat and as I stated, a few of the last F4F4s built reverted to the four guns. Thach said that,"If you can't hit with four, you will miss with eight." The six guns carried 240 rounds for each gun, as I remember, whereas the four guns had 430 rounds per gun. The firing time for the F4F3 was 28.7 seconds and the F4F4 was 16 seconds. Big difference! The USN trained their pilots to shoot in two second bursts which amounted to fifty rounds per gun. The P51B and C had only four fifties and the original F8F had only four fifties and of course the FM2 had the four fifties. The P51s and the FM2s did quite well.

It is also clear, according to Lundstrom, that the pilots trained by the USN had more training in gunnery than the pilots of any other air force in the world. That is not to say that there were not expert gunners in every air force but from what I have read about the RAF in the early war, their pilots were not particularly well trained in gunnery.
 


There appears to be some contradictions within this. If 4 x 0.5 cal were deemed satisfactory why was 6 the norm on US fighters later in the war. It may be true that if you cant hit with four you will miss with eight but it is also true that if you cant hit in 16 seconds you will miss in 29. Many of the long range craft that would attack a British fleet were bombers and the british had already had experience of how how many hits were required to bring down a bomber, that is time you dont have when the bombers are heading towards your fleet and the longer you shoot at a target the longer you are a target yourself.

From the first world war all air cooled machine guns were supposed to be fired for 2 seconds because they overheat, and from the first world war most people in a combat situation forget it.

When American pilots were trained in gunnery, was it with or without a sperry gyro gunsight?
 

The USN's CIC, Admiral King was not noted as an Anglophile... You seem to be suggesting that somehow the perfidious Brits were able to force USN carrier and squadron commanders to retain 6 x .5" MGs in their F4F-4s when it appeared to be a simple field mod to remove one gun from each wing. Then to complete their dastardliness the Brits forced the USN to install 6 x .5" BMGs in their new F6F-3 fighter...

I would submit that the USN studied the combat reports and noted that most pilots came back with ammo remaining and therefore their kill probabilities would increase with more guns to maximize hits per firing pass.
 
I am not suggesting anything. I am relating exactly what Lundstrom has reported in his book about the six guns and the British.. If you have not read the book, I suggest you get it and read it. It is the best researched book I know of on the Pacific air war in 1941-42.

It is obvious that a fighter with six whatever guns is going to be better armed than one with four of the same guns,IF, an adequate supply of ammo can be carried and there is room for the additional guns and IF the ACs performance is not seriously degraded by the extra guns and ammo. In the case of the Wildcat with around 1000 HP, the extra weight of the two guns added up along with some other weight adding measures to seriously degrade the performance. As far as the RAF and there studies of how many bullets it takes to down a bomber, I have read that they decided that it took 197 hits from the puny rifle caliber guns carried by their vaunted eight gun fighters (whoopee) to down a bomber on average. It may have been more than that as I am quoting from an article in Air and Space about the BOB from memory. I have news for you. The 50 BMG is a horse of a different color than the 303 British. The bullet weighs more than three times what the 303 weighs and it's down range velocity and energy is substantially greater than the British weapon. Armor plate that will just stop a 303 will be like hot butter for the 50 BMG. It was and still is a very effective weapon against AC and light armored vehicles, not to mention trucks, locomotives, small ships, houses and buildings and terrorists at a mile.

Quote from Lundstrom, "The First Team", chapter eighteen, the F4F controversy' " Cdr. John Pearson of BuAer's Engineering Section stressed in a letter to Jimmy Flatley that the Bureau never claimed the F4F4 was the perfect fighting machine," The Bureau seemed to feel guilty about the six gun battery- it's reduced ammunition capacity and additional weight. According to Pearson, the decision for six guns with fewer rounds per gun was "very close" inside the Bureau, the deciding point being the need for standardization in production in view of the British insistence on six guns." " The gun controversy became so heated that the Bureau decided to "tamper with production." " Armament labored to redesign the F4F4's fold ing wings to accomodate four guns instead of six and with 430 rounds per gun rather than 240. The resulting air craft, which including a few other minor changes, tipped the scales about 500 pounds lighter than the standard F4F4." Those changes were incorporated in the eleventh Eastern FM1 and those following.

The Mustang, Hellcat, Corsair and P47 could carry six or even eight 50 BMG without serious consequences to their performance although I have read that two MGs were removed from some P51Ds and some P47s to enhance performance both in climb and roll. I also have read that some Corsair pilots would switch off the two outboard guns and just use the four inboard ones and keep the others in reserve.
 
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From what you say above it is clear that the Wildcat with only 1000BHP was marginal on performance despite not seeing combat until over a year after the conflict started. By that time the hurricane II was introduced which had 1480BHP the Mk 1 hurricane was in service from 1938.

The 8 x .303 MGs wernt much vaunted, even before the war started it was thought they wouldnt be hard hitting enough and cannon were preferred. Prior to the Wildcat (martlet) seeing service the RAF were already operating spitfires with 20mm cannon armament which had a hitting power approximately 3x that of a 0.5" MG (in the opinion of the RAF)

The US had even more problems with wing mounted cannon than the Brits which left them with 40 million cannon rounds in storage, eventually they sorted these problems and the last variant of the Grumman range the Bearcat had 4x 20mm cannon which had been standard armament on some RAF fighters for years.
 
There's a big flaw in that argument.

You may obtain a few .50cal hits but fail to critically damage the enemy aircraft. It happened all the time when using machineguns against aircraft. That's why Germany modified the MG151 cannon to fire 20mm mine shells ILO 15mm bullets with only a tiny bursting charge.
 
Renrich
I certainly support everything you say about the effectiveness of the 0.5 vs the 303. 4 x 0.5 would be far more effective than 8 x 0.303 mgs.

Re the British insisting on 6 guns for the F4F4 well I cannot go against Lundstrom but admit to having a question mark about it in my head. I find it hard to believe that the British were insisting on 6 x 0.5 but thats as far as I can go.

You say that the efforts to lighten the Wildcat saved approx 500lb, well the removal of the 2 x HMG would save around 120lb so for anyone to claim that it was the UK's fault that the F4F4 was too heavy is stretching it a bit.

The bit that I totally disagree with is any implication that the UK wanted 6 guns because they couldn't hit anything with 4. That to put it mildly, is total bull. The US may well have put more effort into gunnery training and the average pilot been more accurate when they finished training but that doesn't mean that the other airforces couldn't hit anything. Its worth remembering that the RAF using the Spitfire shot down a good number of aircraft in the ETO using two effective guns as the 4 x 303 were pretty usless against the well protected Luftwaffe aircraft.
 
Wouldn't 2 extra mgs ensure more quickly the destruction of bomber a/c attacking the fleet?
 
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