20mm cannon, best, worst, specs, comparison to LMG, HMG etc. (1 Viewer)

zjtins said:

Sheez no wonder you have problems. ALL wing mounted (not hand held) aircraft .50 were AN versions. Did you honestly think they put D ring handle et al in the aircraft wings????

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You said AN/M3 which is a different gun than the AN/M2.

"The first T25E3 gun was tested at Aberdeen 19 July 1944. The functioning of this gun was greatly improved over that of the T25E1, and the cyclic rate averaged 1,250 rounds per minute. Eight malfunctions occurred, hut for the first time in the development, it was possible to determine the specific cause of each malfunction. A projecting corner on the bolt was responsible for "shorting" rounds in the feedway and causing failures to feed; the remainder of the malfunctions were caused by fatigue of the sear spring. After the satisfactory test's of the T25E3 guns, and to expedite procurement of this weapon, the Army Air Forces requested its standardization in April 1945. Ordnance Committee action was immediately taken to standardize the T25E3 gun as Gun, Machine, Caliber .50 M3, Aircraft, Basic."

"Unfortunately, few M3's saw action in World War II, as only some 2,400 were completed before September 1945. "

BTW, the AN has nothing to do with wing or fuselage mounting. It is a contraction for ArmyNavy, meaning the SAME model gun (or other item) was adopted by Both the Army and Navy.

If you don't believe me try arguing with George M Chinn.

I need to correct one of my previous posting.
When I said no one replaced a 20mm with an HMG I was incorrect. The Fins replaced the 20mm in some of their MS406 with an HMG because of the shortage of spares and ammunition

That was like watching a slow motion car crash

Okay guys. No more bullshit. zjtins is getting two weeks on a beautiful Sahara beach. I asked politely. I'm not asking anymore. We can all post our facts and opinions, but the mamby-pamby crap has got to stop. We can moderate politeness and respect, but we refuse to moderate ignorance. That is where we put trust in our forum members to educate others (including Mods), but in a respectful manner. If posting members do not get the hint, ignore their posts. But whatever you do, don't engage at their level.

I would also like to point out a particular peeve that we Mods have... and that is new members that jump into the forum as if they own the damn place and treat long term members as internet low lifes. That kind of behavior is indicatative of someone who has zero social skills in life and will not be looked kindly upon. You would think that would be simple common sense, but we keep seeing it over and over from what should be grown men with a miniscule of maturity (Note that I used the term men generically, as we do have some women on the forum, but lo and behold they never seem to degrade to this childish level for some reason. Go figure. ).

Okay... back at it.

Only the US relied on HMGs as its primary air to air weapon, because only the US had to. All other nations either manufactured their own cannon or bought theirs from their allies.

Germany -> MG FF/MG FF(M), MG151/15, MG151/20, MK 108, MK 103.

UK -> Hispano Mk II and Mk V

Japan -> Ho-1, Ho-2, Ho-5, Type 99-1, Type 99-2, MG 151/20

Soviet Union -> ShVAK, B-20, YVa, NS 23

Italy -> MG151/20

France -> HS.7, HS.9

Even those nations that had reliable HMGs - Germany, Soviet Union, Italy, Japan - favoured the 20 mm as their primary air to air weapon.

Italy, Germany and Japan even went to HE rounds for their HMG weapons, because HE was found to be MORE EFFECTIVE, than pure kinetic weapons or API.

The Soviet UB 12.7 mm was the premiere air to air HMG of the war. Largest round, highest rate of fire, best ballistics, best packaging, with only minor drawbacks in weight and gun life. Yet, the Soviets clearly favoured the (less reliable and less ballistically favourable) ShVAK and then B-20, which fired the same ammunition. Whenever they could, they moved away from HMGs to 20 mm cannon. LaGG-3 went from 1 x LMG and 1 x 20 mm to 2x20 mm in the La-5/7 and then three 20 mm in the later La-7s when the B-20 was available. Yak family went from 1 LMG and 1 20 mm to 1 HMG and 1 20 mm and then to either two or three 20 mm.

The M2 might have been a 'good enough' solution, but there were much better solutions available, and both the USAAF and USN recognised this fact, before they entered the war and during the war. Otherwise they wouldn't have been working on five different .60 cal designs during the war, two 20 mm projects, a 23 mm project, a .90 cal project and a couple of 37 mm projects, most of which failed to bear fruit.

The US Bureau of Ordinance and USAAF began pursuing the 20 mm as a armament option in 1937, even ordering 400 from overseas and ordering 40,000 into production before Pearl Harbour. The USN settled on the Hispano as its standard weapon in June 1944.

The M2 was a fall back position. It was, even for the USAAF, a second best solution.

zjtins said:

Prove it

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If the British were shooting down axis planes from the summer of 1941 ( started fitting large numbers of 20mm cannon) until the summer of 1944 (started fitting a pair of .50 cal guns in Spitfires only) and the 20mm guns weren't doing the shooting down, what was? .303s or thrown bundles of toilet paper?

zjtins said:

Same to you... where is you proof they ordered only 20mm versions of all aircraft ?

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You do keep twisting or misquoting things. the original statement was "After the Fall of 1944 the NAVY did NOT ORDER an new fighter with .50 cal guns. All fighters armed with .50 cal guns delivered in 1945/46 had been ordered prior to the end of 1944."

All fighters is not the same thing as all aircraft

So lets take it a few at a time shall we.

Jan 25 1944 Vought receives a letter of intent from the Navy to to develop the F4U-4, 5 F4U-1s are to be converted.

April 19th 1944. the F4U-4XA makes it's first flight, July 12 1944 the F4U-4XB makes it's first flight. First Production F4U-4 is completed in Sept/October 1944. In Jan 1945 the Navy is ordering 300 F4U-4Bs with 20mm cannon. All further variations are built with 20mm cannon. Some F4U-4s are built or converted to F4U-4Cs with 20mm guns. The F4U-4 contract was placed in 1944. Please note that it takes until May of 1945 for the first F4U-4s to go into action.

F8F Bearcat. First flew in August 1944, First production plane delivered in Feb 1945, obviously ordered a number of months before that. Some Later -1s delivered with 20mm cannon all-2s delivered with 20mm cannon.

I will go into the jets at a later post.

Any air force tasked with shooting down bombers on a larger scale or destroying air targets quickly used cannons, 20 mm and up. In case of the USN, the 6x0.50 layout was insufficient to effectively counter the kamikaze threat, in case of the USAF, it was night fighting where the 0.50 was found second rate.

It should be mentioned that operational deficiencies of the near pure 0.50 based armament layout of the US were to some extent compensated by the logistic advantages of using a single cartridge for many services and nearly all aircraft. In times of war, logistic aspects are more important than they might appear to be 70 years later on the internet. Personally I don't think the US made a wrong choice by sticking with the 0.50 for as long as they did.

I think the US was right to stick with the 0.5 for WWII but arming jets with the M3 was a step too far. The job of the USAAF post war was to protect the US from bombers, Korea was with respect to the men who fought there a sideshow and meant little to the defence of the US. Knocking down a high flying bomber carrying a nuke is going to be a lot easier with 4x20mm and I am surprised the US never went the same way as the British and French and built a 30mm cannon for bomber killing.

I would note that the USAAF was specifying 20mm cannon (sometimes six) for the planes tasked with bomber interception even before the Korean war. Like the Early F-89s. The USAAF jumped over the 30mm and went to rockets (again mounted on the F-89) and guided missiles. Perhaps they should have gone with a 30mm cannon considering how the rockets and early missiles turned out

While the early F-94s used .50 cal guns it was a "legacy" aircraft, being somewhat of a radar equipped T-33 or two seat F-80.

The US may have had more programs/projects for aircraft guns than any other nation during WW II. Unfortunately sometimes the goals were on the unrealistic side and so were not met. The Browning as a gun had set a rather high bar as far as reliability goes so potential replacements had a hard time in that area. The .50 was adequate but not great and allowed the US more room to try to get things right with some of the potential replacements.

Unfortunately the people responsible kept wanting very large leaps in performance without seeming to understand some basic things about guns, perhaps I am too harsh but they wanted (and spent money and time on) projects that almost required breakthroughs in materials and/or manufacturing processes. AS program after program failed ( or needed time extensions) the .50 continued on with the faster firing .50 being sort of the back up plan.

The high speed .50 cal and .60 cal programs show what I am talking about. High velocity is great in theory as it not only increases striking power but greatly increases the hit chances on maneuvering targets. Unfortunately from the gun point of view there are diminishing returns, it takes about a 20% increase in powder charge for a 10% increase in velocity or a 40% increase in powder charge for 20% more velocity. If you are starting with a high velocity gun like the .50 Browning to begin with the size of the powder charge and cartridge case grow very quickly. The .50 was already known to be a bit of a barrel burner, trying to shove 20-40% more hot gas through the barrel on each shot is going to make things that much worse.
The Americans tried coping the German MG 151 fairly early in the war except they tried to go one better and chamber it for an experimental american .60 cal (15mm) AT rifle cartridge that fired a similar weight projectile as the German round about 200 meters per second faster. the Cartridge case was 18mm longer and bigger in diameter. It could fire a 20% heavier projectile 90mps faster than the Russian 14.5 AT rifle/HMG cartridge.
Obviously it wouldn't fit the original gun and required "some redesign" and it tended to chew up barrels pretty quick.
And so it went.

I admit the thing that really annoyed me was the insistance of proof on things that were so blindingly obvious, a good example being proof that the RAF used 20mm guns from 1941. Apart from a handfull of the ineffective 303 on Spits and Mossies, what else did they use.

Yet when it came to him supplying proof on some totally inept claims what do we get - nothing

Glider, please move on...

"After the Fall of 1944 the NAVY did NOT ORDER an new fighter with .50 cal guns. All fighters armed with .50 cal guns delivered in 1945/46 had been ordered prior to the end of 1944."

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So Shortround where is this proof or reference? I have searched high and low and cant find one.

Not sure how this pertains but the US was always looking for what I believe was 1 shot 1 kill. They were looking early into a French(?) 25mm that never materialized and the 37mm throughout war (many sources). But from what I gather the MV and fire rate was always too low and reliability and number of rounds and or weight were always an issues.

Matt308 said:

Glider, please move on...

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I am but its tempting