USAAF & US Navy Guns since 1930.

[Tony Williams]

Originally Posted by Glider

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.

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

[Tony Williams]

Originally Posted by CharlesBronson

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.

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.

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...

[CharlesBronson]

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...

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.

[CharlesBronson]

75mm guns part II:

[CharlesBronson]

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.

[Graeme]

Originally Posted by CharlesBronson

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

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.

[Graeme]

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...

[CharlesBronson]

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."

Rivets made in china maybe ?

[CharlesBronson]

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.

[Tony Williams]

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.

[CharlesBronson]

Aparently the gun didnt withstand high G in other aircraft either, several accounts of argentine A--4 Skyhawks pilots in 1982 said the gun jammed after some maneouvres evading flak/ fighters.

[CharlesBronson]

MK 12 installation in Chance Vought F7U Cutlass. The sinchronyzation device is emplaced to cut off excessive vibration wich could affected the engines.

[CharlesBronson]

- MK 12 of the A-4AR ( argentine air force A-4M)

- 20x110m U.S.N TP-T ammo ( the 20/66 denomination comes form the 66 calibers lenght of the barrel)

[CharlesBronson]

General Electric M61 multibarreled 20mm Automatic Gun ( GAU-4)


In June 1946, the General Electric Company was awarded the contract for "Project Vulcan". In 1950, GE delivered ten initial model A .60 cal. T45 guns for evaluation. Thirty-three model C T45 guns were delivered in 1952 in three calibers: .60 cal., 20mm, and 27mm, for additional testing. After extensive testing, the T171 20mm gun was selected for further development. In 1956 the T171 20mm gun was standardized by the U.S. Army and U.S. Air Force as the M61 20mm Vulcan aircraft gun.


The M61 20mm Vulcan is an externally powered, six-barrel, rotary-fire gun having a rate of fire of up to 7200 spm. The firing rate is selectible at 4,000 spm or 6,000 spm. The gun fires standard electrically primed 20mm ammunition. The M61A1 is hydraulically or ram-air driven, electrically controlled, and uses a linkless ammunition feed system.

Each of the gun's six barrels fires only once during each revolution of the barrel cluster. The six rotating barrels contribute to long weapon life by minimizing barrel erosion and heat generation. The gun's rate of fire, essentially 100 rounds per second, gives the pilot a shot density that will enable a "kill" when fired in one-second bursts.

The M61 20mm cannon is a proven gun, having been the US military's close-in weapon of choice dating back to the 1950s. The F-104, F-105, later models of the F-106 , F-111, F-4, B-58, all used the M61, as does the Air Force's F-15 , F-16 and F-22, and the Navy's F-14 and F/A-18. The internally mounted 20mm cannon system is common to all versions of the F-15. This system combines the widely used (F-4, F-16, F-18 ) M61 cannon with 940 rounds (A through D models) or 500 rounds (E model) of ammunition. The cannon can be loaded with target practice, armor piercing, or high explosive incendiary rounds. The primary use of the cannon is in the extremely short range (less than 2000 feet) air-to-air environment, where more sophistacated air-to-air missiles are ineffective. Alternately, the cannon has limited usefulness in a ground strafing role.

The M61A1 utilized by the F-14 and F/A-18 aircraft is a hydraulically driven, 6 barreled, rotary action, air cooled, electrically fired weapon, with selectable rates of fire of either 4000 or 6000 rounds per minute. The M61A2 20mm light weight gun is utilized in the F/A-18 aircraft only. The gun system is mated to a linkless ammunition storage and handling system. The F-14 has a capacity of 676 rounds while the F/A-18 has a capacity of 578 rounds of 20mm linkless M-50 or PGU series electrically primed ammunition. World War II fighters and bombers were commonly equipped with Browning M2 heavy barrel .50 cal. machine guns which had a maximum firing rate of 1,200 spm. The Gatling principle permitted a high rate of fire while reducing heat and barrel erosion.

More info to be aded soon...

[CharlesBronson]

Interesting 1942 video showing Bell P-39D Airacobra firing .30, .50 and 37mm guns.