P-39 Aircobra 37mm gun


#1

P-39 Aircobra 37mm gun at Wright Patterson AFB

Here is the Allison engine attached to the end of that gun.


#2

Nice. The Soviet pilots loved this. Both their highest and second highest scoring pilots flew these planes for long parts of their services. I heard the second highest say " I just got the airplane in my sights and pressed the button; it disappeared". He was still flying the plane at the end of the war and some speculate that he was actually the highest scoring pilot but that Stalin would not allow the highest scoring pilot to be flying a US made aircraft. The other fellow switched over to a Soviet plane during the last year of the war.


#3

Awesome display! Awesome information!

Jason


#4

The basic gun is a John M. Browning design, although the adaptation for use with the engine is obviously later. The same guns were also used on some PT boats.


#5

On behalf of giving credit where it’s due, it should be pointed out that the Spad XII of 1917 had a “moteur canon” conceptually very much like the Airacobra, differing in that the P-39’s engine was behind the pilot and the cannon in front of him, the two items being connected by an extension shaft between the aft engine and the forward gear box set just behind the propeller. The gun in the P-39 fired through the hollow propeller shaft. The gun in the Spad was a single-shot, not automatic as in the P-39. Jack


#6

I think the same engine to John.


#7

Motor cannon (i.e. mounted on the engine and firing through the hollow propeller hub, so not needing to be synchronised) were common on interwar French planes. In fact, the 20mm Hispano was originally designed for such an installation, which led to problems when the guns were adopted by the UK and USA and mounted in much more flexible wings.

Germany adopted motor cannon for the Messerschmitt Bf 109 (F series onwards) and a few other aircraft during WW2 and they were also used by many Soviet and some Italian fighters.

For obvious reasons, motor cannon could only be installed on aircraft with inline vee-type rather than radial engines.


#8

This is Pokryshkin ( second highest Soviet Ace according to Soviet authorities) and a good look at his “cobra”. He is center wearing flying helmet. He was later a Marshall of the Soviet Union and head of the Air Forces. He was interviewed in the series " The Unknown War " . Excellent production which should be seen by all. So far as I know all of the ammunition for these guns came from the USA. I would be interested in evidence that the Soviets made any.


#9

That is what I understand also. Furthermore, I believe that only HE ammo was supplied, which further contradicts the former belief that the Soviets used the P39 primarily for “tankbusting” rather than aerial combat.


#10

The AP ammo for this gun was not good for the later tanks. It would have taken out the early ones and did. A rear attack could disable most of the German tanks by destroying the engine which could then be finished off by ground forces. As I understand it although the German fighters were faster they could not out “dog fight” the P39 and the 37mm gun required only a few shots to take them down. The German planes were armed mostly with 7.9 and 20mm guns which required more hits. The 30mm guns came later and fewer planes were armed with them.

Tony knows all about this I think. The Soviet pilots did take down hundreds of German planes with this aircraft and there were reasons.


#11

Here are a couple of bullets used in the gun.

I don’t believe the AP projectile is right for this loading. The crimp ring doesn’t match up.


#12

It looks in the right ballpark. The total length of the loaded M80 AP cartridge is 9.35 inches, and the projectile should weigh 1.66 lbs.


#13

Tony

This round duplicates your OAL and weight specs. Note, though, the crimp divots on the case are north of the crimp ring on the projectile. May be from different lots or manufacturers. Pretty evident that these two pieces were not really meant for each other. I laid it up against the other case. Same-same. No crimp match.

Regards

Rick


#14

The crimping groove is in the right place for the M80 shot, according to the official sectioned drawing of the round which I have.

Comparing the sectioned drawings for the M80 AP and the M54 HE, it looks as if the crimping grooves were in different places (the groove in the case for the M54 is closer to the mouth). If that’s correct, the fact that your cases don’t match up just means that they were used for the HE loading.


#15

Ahhh. Right bullet, wrong case. That makes me feel better. Thanks much for those details.

Rick


#16

Nice ammo Rick!


#17

[quote=“TonyWilliams”]The crimping groove is in the right place for the M80 shot, according to the official sectioned drawing of the round which I have.

Comparing the sectioned drawings for the M80 AP and the M54 HE, it looks as if the crimping grooves were in different places (the groove in the case for the M54 is closer to the mouth). If that’s correct, the fact that your cases don’t match up just means that they were used for the HE loading.[/quote]

Those slugs are what we used to call “monoblock” projectiles. They are a solid piece of steel. Good for a rear shot at the engine of a tank and side shots to knock off tracks but not much use against thick armor on the later tanks.

Our 37mm tank and antitank guns started the war with lots of these shells. Plenty of our men died before the better AP shells showed up in large.

These were much more usefull for aircraft than for ground service.

That display looks to be all APs of this type.


#18

Excellent thread and photos, thank you very much!

Just wish to add, that the first scoring soviet ace - Ivan Kozhedub had actually never flew P-39 Airacobra. He flew only Lavochkins - La-5FN at the beginning of his career (as far as I can remember) and La-7 at the end of the war.
But there are enough soviet aces that flew Airacobra till the end of the war in Europe and they found it very effective fighter plane.
Ivo


#19

That is Soviet revisionist history according to my information.


#20

Well, this is official score, I do not know nothing about unofficial, may be you are right, concerning the lenght of service Pokrishkin was far ahead of Kozhedub, just want to say that Kozhedub had never flew P-39.