Favorites and their achilles heels!

[slaterat]

The British chose the .303 over the .50 because their pre war testing demonstrated that for the equivalent weight of batteries , the .303 did more damage to an aluminum airframe. In the typical 8x .303 vs 4x .50 argument the .303 battery is putting about 4 times the number of projectiles in the air, thats 4 times as many holes in an airframe and 4 times the chance of a critical hit. The fault in the decision lay in the future introduction of light armour and self sealing tanks in combat aircraft which had the effect of greatly reducing the .303 chance of a critical hit, while the .50 would have a much better chance to defeat such protection. The fault in the selection of the .50 is that for not much increase in weight you can get a 20mm cannon which probably has a greater margin of superiority over the .50 then the .50 has over the .303.

Slaterat

 

[Shortround6]

I would wager that if the USN and Marine pilots of 1940 were flying the Hurricanes and Spitfires they would have opted for 4-50 BMGs rather than eight puny 303s.

we have been over this before. I am sure that if those USN and Marine pilots of 1940 had 1942 .50 cal machine guns with 400rpg they would have made that choice. But in 1940 the British would have had the 600rpg version instead of the 800rpg version used by the US in 1942. Loosing 25% of your .50 cal firepower due to the rate of fire difference makes the .303 look not quite so puny. So does cutting the ammo supply back to a near equivalent weight. For the weight of 2800 rounds of .303 (and both the MK I Spit and the MK Hurricane carried less than 2800 rounds) you get about 620 rounds of .50 cal ammo or about 155 rounds per gun of .50 cal. The other aspect of the .50 cal firepower is which ammo would the British have had for the Bob. When did the US adopt the M2 ball? The M1 ball .50 cal ammo had a muzzle velocity several hundred fps lower than the M2 ball ( in fact 2500fps instead of 2900fps but it did use a slightly heavier bullet for a muzzle energy of 10,765ft lbs instead of the 13,000 or so ft/lb of the later .50 cal ammo). Please remember that a MK III Merlin only had 880hp for take-off if operated by the book and not using the 12lb of combat boost. Normal climb was restricted to 2600rpm and not 3000rpm. Adding several hundred pounds of guns and ammo would have improves the firepower of both British fighters but it also would have reduced flight performance.
This changed very quickly as both the MK II Spitfire with the Merlin XII engine and the Hurricane II with the Merlin XX started production during the BoB but the vast majority of the British fighters that fought had the older version engine.

Those USN and Marine pilots of 1940 would have had to choose between the eight puny 303s and four .50 cal guns that fired 25% slower, had about 20% less striking energy per bullet, had a very little difference in flight time to the .303 at practical air to air ranges and had 1/3-1/2 the ammo supply of the 4 gun .50 cal fighters that the US used in 1942.

The whole .50 cal vs .303 thing in the BoB is a red herring. By 1943/44 the situation had changed drastically and the continued use of the .303 is a lot harder (nearly impossible?) to explain.

 

[nuuumannn]

The whole .50 cal vs .303 thing in the BoB is a red herring. By 1943/44 the situation had changed drastically and the continued use of the .303 is a lot harder (nearly impossible?) to explain.

Amen to that. It would be interesting to find how the British came up with the conclusion they did in the paperwork Edgar posted. If British heavy bombers were fitted with .50s rather than .303s, I sure that gunners would have at least felt more confident about attacking the enemy. I was aware that it was pilots who told gunners not to fire on night fighters for fear of giving their position away and not an official source; the RAF weren't that stupid. As well as Leigh-Mallory, Harris was also a strong advocate for arming the bombers with .50s.

An aside; Leigh-Mallory and his brother both died on mountain sides; his older brother George Mallory died ascending Everest in 1924, while Trafford Leigh-Mallory (their father's middle name was Leigh and he later changed his sirname to Leigh-Mallory) died when his Avro York, loaded with his family and belongings on a flight to Ceylon crashed into a mountain side in the French Alps in bad weather in November 1944. In true Leigh-Mallory style, his aircrew had advised against flying in such miserable conditions, but he stubbornly insisted on going, so bringing about his and his family's death. He was on his way to become C in C RAF South East Asia Command. His replacement was Battle of Britain rival, New Zealander Keith Park.

 

[Readie]

The whole .50 cal vs .303 thing in the BoB is a red herring

Precisely. Its another 'what if'....
As you say things changed quickly as WW2 progressed but, in the BoB we had what we had .303's.

John

 

[drgondog]

Remember this discussion of .303 vs .50 was introduced by a memo dated in 1942 arguing the merits of the .303 over a .50 cal and the reference was 'defeat an FW 190'. It lost focus between discussions of more chances for a head shot kill with more ammo, to lack of .50 cal capability at zero deflection, to discussions regarding impregnable frontal armor of the FW 190.

Edgar summarized his opinions as 'littel difference between the two - go with more guns and ammo in the bombers for defense'

BoB wasn't part of the debate.

No test evidence/data displayed in the RAF report posted by Edgar but Juha delivered the Report Kurfust presented regarding actual RAF tests on .303, .50 cal and 20mm - which clearly demonstrated the capability of .50 Cal AP to penetrate fuselage, bulheads, empty skins on fuel tank and still get 30% probability of penetration of the 22mm of duraluminum Me 109 seat/head protection - whereas the .303 was cited as completely innefective. The 20mm was 100% effective.

It is unclear from the Report that the AN/M2 was used, or US API/AP ammunition.

So to reset - Decision made by RAF to continue using .303 for defensive purposes until two years later (1944) - and we are debating this with fairly clear hindsight both with respect to .303 vs .50 and .50 vs 20mm (or 15mm)

 

[pinsog]

The British chose the .303 over the .50 because their pre war testing demonstrated that for the equivalent weight of batteries , the .303 did more damage to an aluminum airframe. In the typical 8x .303 vs 4x .50 argument the .303 battery is putting about 4 times the number of projectiles in the air, thats 4 times as many holes in an airframe and 4 times the chance of a critical hit. The fault in the decision lay in the future introduction of light armour and self sealing tanks in combat aircraft which had the effect of greatly reducing the .303 chance of a critical hit, while the .50 would have a much better chance to defeat such protection. The fault in the selection of the .50 is that for not much increase in weight you can get a 20mm cannon which probably has a greater margin of superiority over the .50 then the .50 has over the .303.

Slaterat

It continues to amaze me that anyone who has seen a .303 or 30-06 next to a .50 in real life could continue to argue that the .30 was a better choice. Again, I would rather shoot an Elephant 1 time with a 400 grain .416 bullet than shoot him 10 times with a .22 long rifle.

People point to the British saying the ".50 was neither fish nor fowl" when compared to the .303 or 20mm, as if the fact that they made the conscious decision to ignore the .50 in the 1930's was the right one. I maintain that, like America not developing a good supercharger or testing their torpedoes, the British simply screwed up.

 

[Readie]

I maintain that, like America not developing a good supercharger or testing their torpedoes, the British simply screwed up.

Either that or economics. We spent our money at RR and Supermarine so. maybe Vickers played second fiddle?
There is another factor, the .303 was the universal British machine gun, tried and tested from 1914 in WW1 and not without a good deal of hitting power in multiple form. Maybe the designers stayed with what they knew?
I'm not defending the .303, just offering an explanation.

John

 

[tomo pauk]

How come that America did not developed a good supercharger???

British might 'screwed up' with .303s for their bombers, but their day/night fighters were 90% cannon-equipped from late 1941 (only Germans carried comparable batteries in the air). Anyway, since the bomber's best policy was not to fire at all, the decision to carry on with LMGs seem like non-issue to me.

 

[nuuumannn]

and we are debating this with fairly clear hindsight...

I think it is universally agreed that the decision not to fit .50s to British bombers was perhaps not the best. It's why it didn't happen that's got everyone talking.

 

[oldcrowcv63]

Re .50s vs .30s, I can only offer examples to suggest that armament that enables the pilot and aircraft to get bullets into the target is what really counts.

- AVG in China and Burma, P-40B, with 2x .50s and 4 wing-mounted .30s with ceiling of 32,400 ft. P-40B did very well vs its IJA opponents.
- USAAF Pursuit Squadron-17 (with PS-20 reinforcements) flying P-40E in Java with its 'improved' battery of 6 wing-mounted .50s possessed both a degraded ceiling of 29,000' and climb rate and couldn't engage bombers and escorts of IJA IJN aircraft flying at higher altitude.
- F4F-3 with 4 x wing-mounted .50s and firing time of over half a minute was felt to be adequate to intercept and counter all IJN opponents in whatever numbers they were encountered. ceiling: 35,000+ ft.
- USN pilots were horriifed to find their F4F-4, with its 'improved' 6x.50s (defined and acquired to satisfy the the RN's FAA) climbed with a rate akin to the TBD Devastator. The -4, even with the increased numbers its folding wings allowed, created a more permeable defensive screen to IJN raiders. ceiling: 30,000+ ft and reduced firing time to less than 1/3rd minute. The decreased ammo supply (to save weight and preserve some performance) made the Grumman a poor defender in the face of large raids. Something the FAA typically didn't need to consider.

Those additional HMG, (heavy indeed) came at a significant performance price that sometimes made the difference between victory and defeat; no matter how much greater or more lethal were the actual gun and ammo.

USN pilots finally got what they wanted in the FM-1 which reverted to the 4 gun battery, but by then, the advent of the F6F and F4U had mitigated the problem.

 

[davparlr]

How come that America did not developed a good supercharger???

I can make a guess. The AAF seemed to favor and fund the development of the turbo to provide high altitude performance, and the Navy did not perceive, nor get, a high altitude threat.

 

[oldcrowcv63]

I can make a guess. The AAF seemed to favor and fund the development of the turbo to provide high altitude performance, and the Navy did not perceive, nor get, a high altitude threat.

I think the USN, with its preference for radial engines, was relatively satisfied with the 2-stage superchargers on its P&W 1830-76 and -86 engnes. The turbocharger was in development strictly for USAAF aircraft with Allison built in-lines as I understand it.

 

[tyrodtom]

The decision not to shoot at nightfighters might have been forced on the Bomber Command pilots by their observation that the .303s very seldom downed the NF. Instead it showed the night fighters exactly where they were.

 

[Shortround6]

People point to the British saying the ".50 was neither fish nor fowl" when compared to the .303 or 20mm, as if the fact that they made the conscious decision to ignore the .50 in the 1930's was the right one. I maintain that, like America not developing a good supercharger or testing their torpedoes, the British simply screwed up.

Once again, the .50 that the British tested and ignored in the 1930s was NOT the .50 cal gun and ammo the Americans were using in Dec 1941 and 1942. They tested the older 600rpm gun (if that, it often failed to reach that figure due to belt drag and/or belt lift problems) with the M1 Ball ammo with it's lower muzzle velocity. The gun and ammo weighed about the same as the later gun (which used the same designation) and cartridge. The higher velocity was th result of new powders which allowed a more progressive burn giving more velocity at the same peak pressure. As an example the US 1906 .30 cal cartridge used over 50,000 lbs pressure to drive it's 150 grain bullet at 2700 fps. The later M2 ball round introduced in the 1930s with new powder could drive the same bullet at the same speed with a peak pressure of a bit over 40,000lbs. Vickrs had offered two if not three different .50 cal cartridges to the government during the 20s and 30s of greatly varying performance. The smallest of which went on to be adopted by the Italians and Japanese army.

The supercharger issue is another red herring. In the 1930s the US superchargers were as good ( or as bad) as anybody elses. British superchargers only took the lead when Hooker went to work on them.

 

[Shortround6]

I think the USN, with its preference for radial engines, was relatively satisfied with the 2-stage superchargers on its P&W 1830-76 and -86 engnes. The turbocharger was in development strictly for USAAF aircraft with Allison built in-lines as I understand it.

With limited budgets (peace time) it didn't make much sense for both services to fund the same research. General Electric had been working on turbos since WW I. Quite a few Curtiss V-12 engines had turbos installed on them during the 20's and 30's and with the B-17 and B-24 the round engines certainly got a large share of the turbos. P&W had a patent for a two stage supercharger in 1937? At any rate, the P&W two stage supercharged R-1830 showed up at the Army 1939 fighter trials in both a Curtiss Hawk airfram and in a Seversky (modified P-35) airframe. Apparently it wasn't quite ready for service as the few performance numbers that have made it to print don't show much advantage.

 

[tomo pauk]

I can make a guess. The AAF seemed to favor and fund the development of the turbo to provide high altitude performance, and the Navy did not perceive, nor get, a high altitude threat.

When one says 'America' and 'supercharger', that would point into both radials inlines, and both Navy and Army AFs, both turbos mech superchargers. With Merlin as the most important exception, what other country/service/manufacturer was providing/operating better superchargers than US planes were equipped with?
The Navy considered (I'd humbly agree) that engine-driven two-stage engines were show stoppers for high altitude threats.

 

[buffnut453]

Those additional HMG, (heavy indeed) came at a significant performance price that sometimes made the difference between victory and defeat; no matter how much greater or more lethal were the actual gun and ammo.

There is one other factor that's being politely ignored in this debate and that's the question of reliability. The RAF's experience with US-provisioned .50 cals wasn't exactly comforting - the Buffalo and P-40 both suffered from frequent gun stoppages, as did the early Mustangs (oh, and the F4F as well!). Those issues were not fully resolved until late 1942 (in the case of the F4F) and even later for the P-51. It's all very well saying, with hindsight, that the .50cal was a better weapon (which, undoubtedly, it did become...eventually) but I think it's folly to suggest that a combat-reliable .50cal weapon installation was available in the late 1930s, or even 1940, such that the RAF, en masse, could have migrated from the venerable .303s.

By the time we get to 1943 or later, the cost of migrating was so huge, because the RAF had expanded so much, as to make the whole question somewhat moot. Would installing .50s on Bomber Command aircraft really have reduced loss rates significantly when the German nightfighters had cannon? I suspect not.

 

[renrich]

To finish up the Lundstrom and Linnekin issue, Lundstrom is the one making the statements regarding how well trained the USN pilots were especially in full deflection shooting compared to other air forces( including the AAF). Linnekin makes no claims of that nature. They both describe gunnery training that the USN used prior to and during WW2 and in Linnekin's case shortly after the war. That description of gunnery training by the two author's is identical. They describe the different full deflection runs using the same terms and the distances involved are the same. Lundstrom also states that the Navy considered the maximum effective range of the 50 BMG as 400 yards. He also states that the USN began to teach full deflection gunnery in the 1920s. He also states that in a head on attack the pilots would open fire at around 600 yards since the firing time would be so short. He also states that the full deflection gunnery runs were seldom able to be used against a fighter but were applicable to use against a bomber. But the constant practise in full deflection shooting gave the pilots an edge when they were forced to take snap shots against a fighter at high deflection numbers.

Lundstrom's books I have read are meticulously researched so I have no reason to doubt his statements in his books especially when I have seen no credible references quoted by anyone on this forum that dispute his claims.

On the other hand, Linnekin was an active duty career Navy pilot who actually flew those full deflection runs in Hellcats, Bearcats and Corsairs and possibly although he does not mention it specifically in F9Fs which he flew operationally in Korea. I actually have never seen "Field Of Dreams" in it's entirety and don't care to. I am not into dreams but would rather deal with facts. I guess sometimes though it is difficult to change our minds when the facts don't coincide with our perceptions.

For those who have Linnekin's book and Lundstrom's I applaud your good judgment and am confident that your purchase will be worthwhile.

 

[fastmongrel]

- USN pilots were horriifed to find their F4F-4, with its 'improved' 6x.50s (defined and acquired to satisfy the the RN's FAA)

Could we finally put this myth to bed the RN FAA was not the main customer for the -4 and its 6 guns. Does anyone really believe that Grumman would upset its main customer by building aircraft to a much much smaller cutomers specs. Does anyone believe that the USN run by noted anglophobe Adm King would allow the RN to dictate its aircraft specs. The -4 was a USN aircraft they got what they ordered and blaming the RN who possibly asked for 6 guns but would have accepted what they were given is a load of rubbish and smacks of buck passing. The 220 (yes thats all) -4 the British bought werent even the same as the USN version having a different engine and other detail differences.

 

[oldcrowcv63]

Could we finally put this myth to bed the RN FAA was not the main customer for the -4 and its 6 guns. Does anyone really believe that Grumman would upset its main customer by building aircraft to a much much smaller cutomers specs. Does anyone believe that the USN run by noted anglophobe Adm King would allow the RN to dictate its aircraft specs. The -4 was a USN aircraft they got what they ordered and blaming the RN who possibly asked for 6 guns but would have accepted what they were given is a load of rubbish and smacks of buck passing. The 220 (yes thats all) -4 the British bought werent even the same as the USN version having a different engine and other detail differences.

Thanks for the contrasting view, Fast. I admit to never hearing it expressed before. Perhaps it's been dealt with in this forum and I just haven't stumbled across it yet. My understanding, perhaps in need of revison, is that Towers, the head of BuAer in 1941, was initially going to produce a lighter, manual wing folding version of its XF4F-4 (with 4 gun armament). However, the RN's FAA insisted on 6 guns per wing for their export model Martlet. He chose to avoid potential production delays of two assemblies by making just the one model that conformed to the RN requirement/request. I blame Towers because he took for granted that the significant British European battle experience was applicable to the lessons his own fleet pilots were learning in their first carrier battles. If he had consulted the pilots I would have less an issue but my understanding is he didn't. British experience in Europe did not translate to that in the Pacific theater and I believe the USN paid a very high price for his decsion. If this is in error, then please advise in what way and please, if you would provide references. I'd very much appreciate it. Thanks.

I don't have any issue with the FAA. I love those guys. they asked for something they wanted because their experience told them it was what they needed. It wasn't our spec, that's all I meant and if I said or implied more, I apologize.

My impression of King is that, next to British citizens, he hated Americans (at least those in the US army), in fact, I think there is some evidence he disliked everyone except maybe Nimitz and even liked him not so much...