USAAF US Navy Guns since 1930.

I admit to not understanding the comment 'The ammunition should be manufactured to fit the chamber of the gun it which it will be fired and not to fit the British or American 20mm. What were they supposed to make.
The estimate of a 15-25 year development period for an optimum aircraft weapon is shall we say, pessimistic, in view of the development period of the Aden and Defta 30mm guns

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Agreed with you. 15 or 25 is ridiculos excessive, the Colt MK-12, gun wich replaced the Hispano An-M3 in Navy usage was developed in just 6 years, between 1946 to 1952.

The ammunition thing is a bit laberynthic, specially when you think that the cases teorically were the same for both US and RAF guns, must be related with the cartrigde overall lenght.

Lockheed P-38 lightning gun installations:

12,7 mm machinegun and 20mm hispano emplacement pictures.

37mm M4/10 gun:

-Characteristing and functioning. The M-10 gun was mostly used in the Bell P-63 and the M4 in the P-39 and few P-38 fighters

-Installation in Bell P-39 showing the early type 15 shots non-disintegrable belt feed box magazine.

-Installation in Bell P-39Q showing the late type 33 shots linkless belt feed "horsecollar" magazine.

37 Browning M4 in P-38 and XFM-1.

Despite the fact the M4 is related almost exclusively with the P-39 airacobra it was used in some other tipes like the experimental XFM-2 Airacuda and early models of P-38 Lightning.

The Airacuda was a very strange aircraft. The design's hypothesis was that it would he used as a bomber-destroyer. It had thirty-seven millimeter cannons, one in the nose of each nacelle, but little in the way of defensive weapons. Several other innovations were being explored on the Airacuda that were not used on any previous military airplanes.
Because some of the innovations were impractical, they haven't been used since.

The primary function of the men in the nacelles was loading the guns, although they could be fired by the gun crew in an emergency. Initially, the pilot of the plane aimed the airplane in the general direction of the formation. Further correction in aim would then be made by the gun control officer, and fired by him. His station was directly behind the pilot, using an inverted periscope that came out through the belly of the ship to aim the guns. The fire control officer would clutch the guns into the gyros, which stabilized them. From that moment on they would stay on target. The person operating the guns could then make any further correction and fire away until the bomber was brought down. His position had swing-out flight controls and in an emergency he could fly the airplane.

- Lockheed P-38D, nose.

- Bell XFM-1 nacelles.

- Bell XFM-1, detail of gun mounting with coaxial .30 caliber MG.

M9 37 mm cannon.

Despite it followed the lines and principle of functioning (long recoil) of its predecessors, the M9 was a completely new design made around a larger, powerful, high velocity ammunition used in the infantry 37mm M1 AT gun..

The Bell P-63D Kingcobra, the only aircraft ever equipped with M9 high velocity gun, it was also the one-of-a-kind since there were no production series of this atractive, bubble canopy equipped fighter, Single prototipe made in 1944. Note the long barrel overhang in this A/c.

A handful of M9 guns were also used in PT boats.

37x145R ammo for M4/10 guns.

Medium velocity round, it used a percussion fire, rimmed straight case.

High-explosive shell, 37 mm, M54 standard



This shell uses the point detonating fuse, M56. The complete round weighs 1.99 pounds (900 g); as fired, the projectile weighs 1.34 pounds (608 g). The 0.16-pound (70 g) charge of M2 powder is a Hercules NG formula of single perforated grains with 0.030 inch (0.76 mm) web and gives the projectile the prescribed muzzle velocity of 2,000 feet per second (600 m/s).

The M54 features the shell-destroying tracer in addition to the point-detonating fuze. The tracer, which has a burning time of three seconds, sets off an igniting relay charge of 1.68 grains (0.109 g) of Grade A-5 Army Black Powder which ignites a relay pellet to detonate the charge and destroy the shell before ground impact.

The bursting charge of tetryl weighs 0.10 pound (45 g), and the alternate Composition "A" charge weighs 0.105 pound (48 g). The tetryl loading consists of a 200 grain (13 g) tetryl pellet pressed into the shell cavity under 9,000 to 10,000 psi (60 to 70 MPa) pressure and the remainder of the charge of two equal increments pressed under approximately 9,000 psi (60 MPa) pressure. The Composition "A" bursting charge is loaded in the same manner as the tetryl charge, except that the relay pellet with the Composition "A" weighs 36 grains (2.3 g) as against 23 grains (1.5 g) for the pellet used with the tetryl load.


Practice shell, 37 mm, M55A1 standard



This shell is the high-explosive shell modified slightly for practice purposes. It contains a red tracer and a dummy fuse, M50, M50B1, M50B2 or M50B3. The M50 dummy fuze is made from a plastic composition and M50B1, M50B2 and M50B3 fuses are made from low carbon steel machined to give the same contour and weight as the point-detonating fuse, M56, used with the M54 projectile.

As used in the automatic gun, M4, the complete round weighs 1.99 pounds, and as fired the shell weighs 1.34 pounds (610 g). The 0.16 pound (70 g) charge of M2 powder is Hercules NG formula of single perforated grains with a 0.030 inch (0.76 mm) web and gives the prescribed muzzle velocity of 2,000 feet per second (600 m/s).

Armor-piercing shot, 37 mm, M80 standard



The weight of the complete round is 2.31 pounds (1.05 kg), the weight of the A.P. shot is 1.66 pounds (750 g). The propelling charge is 0.15 pound (78 g) of M2 powder of a Hercules NG formula with a single-perforated grain and 0.030 inch (0.76 mm) web. The shot is a monoblock projectile with a tracer element of three seconds burning time and has no fuse or bursting charge.

Penetration 20 mm rolled plate at 460 meters (500 yds)

Rounds and magazine in P-39D.

37x223SR cartrigde for M9.

It used a slim bottlenecked case with percussion primer, 3 types of amunition: armor piercing with tracer, armor piercing with ballistic cap and he explosive, target practice tracer.

Projectile weight 780 to 810 grams, muzzle velocity 880 to 910 mps.

37x223Sr compared with russian 37mm AAA and german 37 BK-3,7 ammo ( used by Rudel´s Gunship)

The 75 mm family of airborne cannons. ( 1 )

Serie of heavy guns manually loaded derivated from the artillery piece M1897, initially were aimed for grouns attack but then were used mostly in the anti-shipping role with some succes in the Pacific teather of Operations.

Glider said:

I know its a bit of a cheek but this smells like a cover up. The USA knew from about 1942 what the problem was with the 20mm produced in the USA. All they had to do to get it working was to adapt the American production to cater for the changes introduced by the UK.

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I agree. I've summarised the problems and remedial actions and added some comments of my own here: Modifications and Attempts at Standardization

CharlesBronson said:

Agreed with you. 15 or 25 is ridiculos excessive, the Colt MK-12, gun wich replaced the Hispano An-M3 in Navy usage was developed in just 6 years, between 1946 to 1952.

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Not the best example, as that was only a 20mm M3 modified to take the more powerful 20x110 USN ammunition and speeded up somewhat.

The ammunition thing is a bit laberynthic, specially when you think that the cases teorically were the same for both US and RAF guns, must be related with the cartrigde overall lenght.

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I now believe that the RAF's 20mm ammunition was probably coated in hard wax at the factory to provide lubrication. That way, they didn't have to grease the cartridges when loading them, as the Americans did.

P.S. I seem to recognise some of those ammo photos...

I now believe that the RAF's 20mm ammunition was probably coated in hard wax at the factory to provide lubrication. That way, they didn't have to grease the cartridges when loading them, as the Americans did.

P.S. I seem to recognise some of those ammo photos...

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Thanks for the info and sorry I didnt quote your site before.

Cartrigde color images on page 2 are from:

Untitled Document

Signed CharlesBronson the amable thief.

Cal .60 T17 heavy machinegun.

Weapon wich was inspired by the german MG 151 family, with a 15mm projectile, short recoil operated and electrical primer cartrigde. Despite the long development programme, money and effort put on it remains as an experimental armament only.

CharlesBronson said:

using an inverted periscope that came out through the belly of the ship to aim the guns.

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Hi Charles. As illustrated...

Regards the 37mm cannon, I've read that when fired (from Airacuda) the ORIGINAL non reinforced airframe "shook". When the side mounted 0.50s were fired, "rivets popped and the skin wrinkled and fractured."
Eventually Bell invented a hydraulic shock absorbing gun mount that was simple, lightweight and allowed the machine guns to recoil 5/8" every time they were fired.

And again!

Bell's XP-83 must have incorporated nearly every US gun in project form?

One proposal included four 20mm cannon. Another was four 37mm cannon and one was for TWENTY 0.5in machine-guns.
Eventually six Browning 0.5in machine-guns were selected but with an elongated nose there was serious consideration to use six 0.6in machine-guns...

Vey nice, thank you for the photo and drawing.

Regards the 37mm cannon, I've read that when fired (from Airacuda) the ORIGINAL non reinforced airframe "shook". When the side mounted 0.50s were fired, "rivets popped and the skin wrinkled and fractured."

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Rivets made in china maybe ?

US Navy MK 12 20 mm cannon.

This gun was derivated from the late Hispano Suiza guns, the Navy insisted in higher muzzle velocity and rate of fire, for wich a new cartrigde was introduced in inventory.
The operation iS a reciprocating recoIl with assisted gas unlock for opening the breech.

It used a lighter projectile with a bigger charge for better muzzle velocity and faster rate of fire at the cost of hitting power. It entered U.S. Navy and U.S. Marine Corps service in the mid-1950s, replacing the Navy's earlier M3 cannon.

Rate of fire exceeed the 1000 rpm. Muzzle velocity 990 to 1020 meter per second.

In service, the Mk 12 proved less than satisfactory. Although its muzzle velocity and rate of fire were acceptable, it was inaccurate and frequently unreliable. Pilots of the F-8 Crusader over Vietnam, in particular, appreciated the presence of the cannon, but jams and stoppages were common, especially following hard dogfighting maneuvers.

Nevertheless, the Mk 12 was standard cannon armament on gun-armed Navy and Marine Corps fighters from the early 1950s to the early 1960s, including the F4D Skyray, F3H Demon, A-4 Skyhawk, F-8 Crusader and Navy versions of the A-7 Corsair II.

Mk 12 installation in Grumman F-11F1.

The problem wiith the MK 12 gun installation in the F-8 Crusader was the distance between the ammo tanks and the guns, which meant thhat long belt runs were needed. G-forces in violent manoeuvring would cause the ammo belt links to pull apart.