.50 cal machine guns vs 20 mm autocannons on US aircraft

[Glider]

The AAF liked the 50BMG because it allowed for 6-8 guns with a lot of ammo which enabled the pilot with not great gunnery skills more opportunity to get hits. The USN came around to the point of view that the 20 MM cannon would make a better armament package. Perhaps their POV was influenced by possibly more emphasis on gunnery skills in USN pilot training. Just my guess. The AAF's and USN's opinions were stated in the "Report of the Joint Fighter Conference, 1944."

Going from memory the main arguement for the Navy wanting 20m was because they could do the same amount of damage in a shorter period of time with 4 x 20mm than 6 x HMG. An important point if the enemy is heading for a carrier which can be put out of action with one hit, resulting in you starting to remember the ditching instructions

 

[davparlr]

So I'd say pilots praised what they had, and they had only the fifties.

They don't if they don't don't work, and the 50s worked.

Does anyone have a report from the Germans or Japanese saying they were not concerned about the American fighters because they only had 50s?

 

[davebender]

If someone is shooting at me I would be concerned even if it's only a BB gun. But I would be a lot more concerned if they are firing a 3cm Mk108 cannon.

 

[Shortround6]

I think that is an over simplification.

The American pilots didn't have anything to compare to. Very few flew planes that had .30 cal guns and very few flew planes with 20mm cannon so they had nothing to compare the .50s to.

Any pilot who is not concerned about any enemy aircraft regardless of it's armament is a fool. Even a .30 cal bullet can cut an oil line and keep a pilot from getting home, doesn't mean the .30 cal gun is a plane killer as the British found out in the BoB.

The American battery of .50s "worked" but it was heavy for it's target effect. A lighter weight but just as effective (or more effective armament) would have allowed better performing aircraft (Better climb or turn or better range or pick something) without decreasing the effectiveness once on target.
The American .50 cal battery "worked" against the targets it came up against but the vast majority of targets weren't actually all that tough.

 

[davparlr]

I think that is an over simplification.

The American pilots didn't have anything to compare to. Very few flew planes that had .30 cal guns and very few flew planes with 20mm cannon so they had nothing to compare the .50s to.

Did the Brit P-51B/D pilots complain about the ineffectiveness of the 50s and demand 20mm be installed? I have not seen any, but, of course, I may just not know.

Any pilot who is not concerned about any enemy aircraft regardless of it's armament is a fool. Even a .30 cal bullet can cut an oil line and keep a pilot from getting home, doesn't mean the .30 cal gun is a plane killer as the British found out in the BoB.

But there were complaints that the 30s were not effective, or they never would have changed them.

The American battery of .50s "worked" but it was heavy for it's target effect. A lighter weight but just as effective (or more effective armament) would have allowed better performing aircraft (Better climb or turn or better range or pick something) without decreasing the effectiveness once on target.
The American .50 cal battery "worked" against the targets it came up against but the vast majority of targets weren't actually all that tough.

This is a tiring argument and redundant to other threads. The 50 cal armament was indeed heavy and had less hitting power than larger cannon. However, they were available, produceable, reliable and effective. The decisions at the time was based upon the effectiveness verses performance impact, the production line impact of selecting another weapons system, and the analysis of probability of hits versus experience of the pilot. To claim now, with no risk in the answer, that this decision was incorrect and that the 50s, mounted in American aircraft, were not devastatingly effective against the targets faced is ludicrous and ignores history.

As far as ineffectiveness against tougher targets, is there any combat evidence that they wouldn't be or is it just supposition?

As far as I have read, neither the AAF, Navy, or British fighting forces demanded the removal of 50s and the installation of the cannons, but I am certainly open to being enlightened.

My opinion is that the American military decisions concerning the 50s was correct and, for the most part, the American weapons systems had excellent results for the jobs they were intended.

 

[Edgar Brooks]

Did the Brit P-51B/D pilots complain about the ineffectiveness of the 50s and demand 20mm be installed? I have not seen any, but, of course, I may just not know.

If they did, it would have been reported privately to Leigh-Mallory, who'd already got quite narked about not being given the .5" in the Spitfire, as early as 1942.

As far as ineffectiveness against tougher targets, is there any combat evidence that they wouldn't be or is it just supposition? As far as I have read, neither the AAF, Navy, or British fighting forces demanded the removal of 50s and the installation of the cannons,

I don't know about combat evidence, since an unhurt German pilot would have got away, and the RAF pilot couldn't be sure what damage he might have effected. However, in tests on German armour plate, it was found that the .5" had no more penetration than the .303", especially as they could both be toppled as they went through the fuselage skin. This was the reason for the RAF sticking with 4 x .303", rather than having 2 x (slower-firing) .5", coupled with their cannon, since the average pilot wasn't a very good shot, and, in a deflection shot (always the most difficult) the "scatter-gun" approach was more likely to disable the pilot; the change of mind came with the introduction of the gyro gunsight, which made even ordinary pilots into crack-shots, so the "E" wing was born, but not until 1944.

 

[Glider]

I don't know about combat evidence, since an unhurt German pilot would have got away, and the RAF pilot couldn't be sure what damage he might have effected. However, in tests on German armour plate, it was found that the .5" had no more penetration than the .303", especially as they could both be toppled as they went through the fuselage skin. This was the reason for the RAF sticking with 4 x .303", rather than having 2 x (slower-firing) .5", coupled with their cannon, since the average pilot wasn't a very good shot, and, in a deflection shot (always the most difficult) the "scatter-gun" approach was more likely to disable the pilot; the change of mind came with the introduction of the gyro gunsight, which made even ordinary pilots into crack-shots, so the "E" wing was born, but not until 1944.

Before the war the RAF recognised that the 303 wasn't a long term solution and the weapon they wanted was the 20mm. The decision to go for 8 x 303 was a holding position until the 20mm was available. Once the 20mm was available that was always the primary weapon. Its worth remembering that the 4 x 303 in the Spitfire was replaced with 2 x HMG before the Gyro gunsight was in full production and that pilots sometimes removed some of the LMG both to try and improve roll rate, and because the LMG was ineffective. You never hear of the 0.5 being removed to improve roll rate.

As an aside the Beaufighter had its 6 x LMG replaced by 4 x 0.5 when weapons were retained in the wing.

 

[davparlr]

However, in tests on German armour plate, it was found that the .5" had no more penetration than the .303", especially as they could both be toppled as they went through the fuselage skin.

Interesting since the 50s are often used against light armor.

This was the reason for the RAF sticking with 4 x .303", rather than having 2 x (slower-firing) .5", coupled with their cannon, since the average pilot wasn't a very good shot, and, in a deflection shot (always the most difficult) the "scatter-gun" approach was more likely to disable the pilot; the change of mind came with the introduction of the gyro gunsight, which made even ordinary pilots into crack-shots, so the "E" wing was born, but not until 1944.

This was the same rationale that the AAF used in support of their usage of the 50s even after the advent of the gyro sight.

 

[Edgar Brooks]

Its worth remembering that the 4 x 303 in the Spitfire was replaced with 2 x HMG before the Gyro gunsight was in full production .

That's a myth, since the IIC (bomber) and IID (fighter) sights were in production in late 1943, and the Spitfire E wing, with a single .5", was not produced until March 1944. American production (of the K-14 Mk.18 versions of the Ferranti sight) might have started after the U.K., of course, since they first had to see it tested, then formally accept it.

pilots sometimes removed some of the LMG both to try and improve roll rate, and because the LMG was ineffective. You never hear of the 0.5 being removed to improve roll rate

While true, it was found, in tests, that removing the guns had little effect, and, though permitted, the practice was discouraged. The main protagonists seem to have been the Poles, who were famous for their desire to get in close, to make sure, and where the "popgun" .303" gave no advantage. Removing the .5" would have had no effect, whatsoever, since it was so much closer to the fuselage

 

[Kryten]

two issues of note here, when considering the .303, we all tend to forget the volume of fire these guns produced, 8x 1200rpm is 9600rpm, that puts the volume of fire above a regular modern mini gun, I dont think many of us would want to be in a Me109 hit by a mini gun! bombers with more armour would have been able to soak up that kind of fire but a fighter certainly would'nt shrug it off!
secondly, the .50 is a particularly nasty bit of kit, having puched holes through a BMP IFV with an.50 I can vouch for its firepower, again being in an aircraft hit by six or eight of these would be a sobering experience!
I think we tend to grossly undrestimate the damage that HMG can do when comparing it to cannons!

 

[renrich]

This debate (argument) has been had before with little accord being reached. I have stated this many times. The 50 BMG is a very destructive round with desirable ballistic properties. I have fired one on the range at Fort Hood and seen what it will do against old vehicles. The four fifites in F4F3s put a IJN DD out of action just prior to the Coral Sea. The USN remarked that the 50s were very effective against light Japanese vessels in the Pacific, including DDs, patrol craft and freighters. We all have seen combat film of P47s and other US AC destroying locomotives in Europe and Japan with 50s. The M2 50 and it's ammo was ubiquitous all over the world where the US fought WW2. It was reliable and it's use by all of the US military simplified logistics. Butch O Hare, destroyed or badly damaged six Betties with the four guns and 420 rounds each in the F4F3 while protecting his carrier. The USN did not like the F4F4 with 240 rounds each for it's six guns partly because of the low ammo capacity. It was a severe handicap for the Zekes at Midway with only 60 rounds per 20 MM cannon.

There is no doubt that on average a hit from one 20 MM round will yield more damage to a target than a hit from one 50 BMG round. If I am defending my sinkable air base though and if I am a good gunner, I might prefer four or six fifties with 400 rounds per gun or more than four 20s with around 120 rounds each. The firing time for the F4F3 was 28.7 seconds. The firing time for the P51 with 20 mm cannon was 12.5 seconds. That 16 extra seconds could come in handy.

 

[vanir]

The 50 BMG is a great gun. Obviously it's an excellent gun or it wouldn't have been so copied. The only argument against it is being a 1934 gun. In 1944 the Beresin was better (edit. note because of rechambering option to 2cm, trumping the BMG on weight/performance ratio).
Swap out american brownings for beresins and nobody would have a leg to stand on.

The argument on aero armament is only two: can it deal with the typical target on sorties of its interceptor? what is the performance to weight ratio? The fifty only loses on weight/performance ratio and only after 44 given it already had one modernisation improving performance, then had another in 44 but it was still heavy by then.

 

[Shortround6]

Did the Brit P-51B/D pilots complain about the ineffectiveness of the 50s and demand 20mm be installed? I have not seen any, but, of course, I may just not know.

I am sure there were a number of complaints about the P-51B armament, of course mostly in area of it not functioning.

But there were complaints that the 30s were not effective, or they never would have changed them.

Several points here.
1. you made a statement about pilots being unconcerned about planes armed with .30 cal guns. a rather bogus argument.
2. I did say that the .30 cal was not an effective armament "doesn't mean the .30 cal gun is a plane killer as the British found out in the BoB"
3. Do not confuse cause and effect, British were planning on changing to cannon before 1938, but it took time. They did NOT change to canon as a result of complaints from pilots during the BoB. Not to say that complaints weren't made.

This is a tiring argument and redundant to other threads.

You are right, this argument is tiring argument and redundant. But some people can't seem to grasp that the .50 cal gun, even in multiples, was not the be all and end all of aircraft armament. The US spent a lot of money and engineering time trying to come up with a replacement. Why bother if the .50 was so good or doing everything they wanted? I am referring to the .60 caliber program/s and the high velocity .50 cal programs ( most of which would require new guns) and the multiple programs to boost the rate of fire of the basic M2 Browning which finally bore fruit in the spring of 1945.

However, they were available, produceable, reliable and effective. The decisions at the time was based upon the effectiveness verses performance impact, the production line impact of selecting another weapons system, and the analysis of probability of hits versus experience of the pilot.

Available and producible they were. Reliable tended to vary with the installation and the year, with better trained armorers and more experience the .50 did reach an enviable state of reliably in general. Effectiveness is still debatable. The Americans did produce tens of thousands of 20mm guns that due to ordnance pig headedness were essentially useless. If the US had wanted more 20mm guns I am sure that ONE .50 cal factory could have been changed over. As far as " the analysis of probability of hits versus experience of the pilot" goes, that was a big part of the push for the .60 cal and HV .50 cal programs. To increase the probability of hits for the average pilot.

To claim now, with no risk in the answer, that this decision was incorrect and that the 50s, mounted in American aircraft, were not devastatingly effective against the targets faced is ludicrous and ignores history.

Hardly, as far as now and no risk goes, the Navy wanted 20mm cannon, as has been shown in other threads. 20mm guns were also the preferred armament for night fighters, from the P-70 (A-20) on up. Some prototype aircraft were specified with 20mm guns.
This certainly shows that the interest in other armament besides the .50 was there and that for fleeting targets (short engagement times) and larger targets (night bombers?) the 20mm may have been preferred. The fact that the Japanese failed to up with better protected planes or that the Germans were fielding predominately singe engine fighters in the later part of the war certainly helps with the the .50 cal being "devastatingly effective against the targets faced" but depending on your enemy to field small, light aircraft that suit your armament is hardly the mark of good planning or evidence that your armament is really up to world standard.

As far as I have read, neither the AAF, Navy, or British fighting forces demanded the removal of 50s and the installation of the cannons, but I am certainly open to being enlightened.

I am willing to be enlightened also. I am not sure what you mean by "demanded the removal". as far as I know very few airplanes, once they left the factory, had their guns taken out and replaced by other guns in the field. The ones I do know of were usually american planes (like Brewster Buffaloes) where the .50s were taken out to be replaced by .303s, much more due to ammo shortages and an attempt to improve flight performance by lighting the airplane than any real thought that the .303 was a better gun/round.

My opinion is that the American military decisions concerning the 50s was correct and, for the most part, the American weapons systems had excellent results for the jobs they were intended.

That is your opinion and while it certainly simplified logistics and training and did manage to do the job required the American .50 did have the major drawback of being very heavy for what you got out of it. as for the second part of the sentence, many american weapons systems did provide excellent results, but just because many did does not mean all did and it doesn't mean that better results could not have been achieved by a different weapons system. The US has been notably ill served by many of it's small automatic weapons. The BAR was a good automatic rifle in 1918, it was a poor light machine gun in WW II. The M-14 was a joke in full automatic fire and suffered from a number of problems in it's "intended" role even if it performed many other roles/duties well we are still living with the problems of the M-16 and the early M-60s had enough design flaws to make some people wonder if the designers had been paying attention at all to how machine guns were used.

 

[Shortround6]

If I am defending my sinkable air base though and if I am a good gunner, I might prefer four or six fifties with 400 rounds per gun or more than four 20s with around 120 rounds each. The firing time for the F4F3 was 28.7 seconds. The firing time for the P51 with 20 mm cannon was 12.5 seconds. That 16 extra seconds could come in handy.

I really like the " four OR six fifties with 400 rounds per gun " bit, only a difference of 167 kg of weight just for the guns and ammo. I also like a weight of 1150lbs of 50 cal guns (six) with 400rds apiece is equal to a weight of around 780lbs, four 20mm Hispanos with 120 rounds apiece. I wonder what happens if the weights are a bit more equal, like 1080lbs for the 20mm guns and ammo? 240 rounds apiece? 24 seconds of firing time? Or if the Six .50 installation is held to the 780lb weight of the of the 20s with 120rpg? 211-212 rpg for a firing time a bit over 16 seconds?

the .50s are always going to have an advantage if they are allowed an gun and ammo weight 47% higher than the 20mm gun and ammo weight.

 

[renrich]

The point is that the USN much preferred the four gun with more than 400 rounds per gun installation of the F4F3 over the six gun with 240 rounds of the F4F4 to the point that the late F4F4s switched back to the four guns as well as the FMs. The Hellcats and Corsairs carried the six guns with 400 rounds without much performance penalty. It is apparent that firing time was important to US pilots. Perhaps it did not matter as much to British and German pilots and the reason might have been that their AC could not stay in the air as long as the US models. Shorter duration flights don't need as long firing times. If you are going to be in the air for four hours or more it is nice to know that your ammo supply may be adequate. A fighter with empty guns is useless. If you read "The Shattered Sword" the Zekes having to land continually to replenish the 20 mms during the attacks from the AC based on Midway had a major impact on the eventual outcome of the battle. I have read that in the Pacific some Corsair pilots would switch off two guns until the other four ran out in order to stretch out firing times. Does not seem logical to me to simply ignore the huge difference in firing times for the P51 with 20mms and the F4F3 with four fifties.

 

[tomo pauk]

Zeros, during the Midway, were armed with cr@ppiest 20mm cannon, both in technical sense (ballistics, RoF) and in tactical (rpg/firing time). So this does not make a case against 20mm cannons.

For 1943 and later US fighters, a weapon along the lines of Shvak (4 instead 6 or 8 HMGs) could've lead to increase of rounds per gun carried, not decrease, for same volume allocated for ammo.

 

[vanir]

four beresins have the weight of four BMG but can use 2cm ammo boxes. That's a lot of firepower you can pop in any FM-2 without affecting its performance. Imagine four 2cm per wing in a thunderbolt without a loss in aircraft performance. That's more than 10 shells per tenth of a second firing time. You can do so much with that.

 

[davparlr]

Several points here.
1. you made a statement about pilots being unconcerned about planes armed with .30 cal guns. a rather bogus argument.

I don't think I said this. What I said was "Does anyone have a report from the Germans or Japanese saying they were not concerned about the American fighters because they only had 50s?"[/QUOTE]

2. I did say that the .30 cal was not an effective armament "doesn't mean the .30 cal gun is a plane killer as the British found out in the BoB"

I don't understand this. Did you mean "doesn't mean the .30 cal gun is not a plane killer…}

This is a tiring argument and redundant to other threads.
You are right, this argument is tiring argument and redundant. But some people can't seem to grasp that the .50 cal gun, even in multiples, was not the be all and end all of aircraft armament.

I don't understand why you keep saying this. I haven't seen anyone say it was a super weapon or a "be all and end all of aircraft armament".

The US spent a lot of money and engineering time trying to come up with a replacement. Why bother if the .50 was so good or doing everything they wanted? I am referring to the .60 caliber program/s and the high velocity .50 cal programs ( most of which would require new guns) and the multiple programs to boost the rate of fire of the basic M2 Browning which finally bore fruit in the spring of 1945.

I don't understand this argument. During war time lots of money and time go into advancing the current capabilities. What other weapons system could you apply you philosophy that spending money and time on improving was a sign of lack of capability, engines like the Merlin, airframes like the Fw-190, bombs, tanks????

As far as " the analysis of probability of hits versus experience of the pilot" goes, that was a big part of the push for the .60 cal and HV .50 cal programs. To increase the probability of hits for the average pilot.

And one of the reasons of why the 50s was kept by the AAF instead of 20 mm.

Hardly, as far as now and no risk goes, the Navy wanted 20mm cannon, as has been shown in other threads. 20mm guns were also the preferred armament for night fighters, from the P-70 (A-20) on up. Some prototype aircraft were specified with 20mm guns.

And yet I showed on another thread that the effectiveness of the F-86, with six M3 machine guns, was as effective as the F9F with four 20 mms, in addition, one poster indicated that the weight including ammo, was similar.

I do know that, in the late 1970s, there was a proposal to upgrade the two F-5 M-39 20mm cannons to a 50 cal Gatling. The armaments guy had said there was evidence this would be a more effective air-to-air weapon. When quickly looking at the two compared to what I had looked at on the F-86, it looked as if the exchange was basically awash with a slight advantage going to the Gatlin. It went nowhere because, I suspect, nobody wanted to develop a new aircraft gun.

The fact that the Japanese failed to up with better protected planes or that the Germans were fielding predominately singe engine fighters in the later part of the war certainly helps with the the .50 cal being "devastatingly effective against the targets faced" but depending on your enemy to field small, light aircraft that suit your armament is hardly the mark of good planning or evidence that your armament is really up to world standard.

Do you have evidence that a P-51D or P-47 would not have been devastatingly effective against, say, a B-17 or B-24, or is this supposition?

Certainly by the end of WW2, the M-2 armed fighters were not up to world standard. However, had the M-3 been incorporated they would have been. Indeed, the M-3 armed F-86 was as potent as the F9F and more so than the Mig-15. This all changed with the M-39 20 mm.

I am willing to be enlightened also. I am not sure what you mean by "demanded the removal".

Not adequate to do the job like there was a big demand to upgrade the F4F once the Zero was encountered.

The BAR was a good automatic rifle in 1918, it was a poor light machine gun in WW II.

I know very little about combat weapons. I am sure others here are much wiser than I am. The BAR was heavy and did not have a replaceable barrel, I think. Heavy seems to be important for the power it possessed since the M-14 was critized for being too light to replace it.

The M-14 was a joke in full automatic fire and suffered from a number of problems in it's "intended" role even if it performed many other roles/duties well

The M-14 seems well liked but out of place in the jungle as any full sized rifle would be. In the Middle East it seems to be popular.

we are still living with the problems of the M-16

It seems to have been around a long time for such a miserable failure.

and the early M-60s had enough design flaws to make some people wonder if the designers had been paying attention at all to how machine guns were used.

I have no idea.

 

[renrich]

The Japanese 20mm was a copy of the Oerlikon with a short barrel to save weight and only had a 60 round magazine. But since the 20mm was their most effective weapon the Zekes had the IJN CVs were kept busy recovering, rearming and relaunching the Fighters to cope with the onslaught of the Midway based AC. Since the flight decks were being used the Japanese could not ready another strike to be launched. The Japanese attack planes had to get to the flight deck before the ordnance could be armed and the engines warmed up, unlike the US CVs with the open hangar decks. According to "The Shattered Sword" which seems to be the best and most recent version of the battle, that was the reason the US VSBs and VBs were able to enjoy such success. The small magazine capacity was the problem, not the gun itself or the ballistics. A Wildcat, SBD, Avenger or B26 with a Zeke on it's tail with only 30 cal mgs was very difficult to shoot down.

 

[Trilisser]

Some information from Finnish sources indicate that the .5 M2 suffered from terribly low barrel life if the rate of fire wasn't kept down (well below 600 rpm)...