Ordnance Of The Week: Colt anti-tank .90 caliber Automatic Weapon, 1941
The Experimental .90 caliber cannon was designed by engineers working for the US Ordnance Department with work beginning in 1937. There were four designs in various configurations with differing actions and feed mechanisms in development by numerous companies under the Ordnance Department’s direction concurrently, these were designated the T1 to T4, the weapon pictured above is the final incarnation, the T4. The first three prototypes were intended to be the main armament for aircraft. However, they were all subsequently rejected due to a variety of issues including being too heavy and suffering from slow rates of fire. The development of these aircraft cannon designs continued concurrently until the project was discontinued in 1940.
Cal. .90 Automatic Aircraft Cannon, Model T2, (source)
The T4, the last of the experimental cannons was also intended to be an aircraft cannon however, by 1941 when the above photographs were taken, it had been repurposed as a anti-tank weapon. At first glance the T4 looks like a scaled up Browning .50 caliber M2 machine gun, but instead it is chambered in a huge .90 caliber or 23mm round which weighed 0.45 lbs and used a long-recoil operation similar to that used in Browning’s original 37mm Autocannon.
With the shortcomings of the T1-3 now obvious and need for aircraft guns was mostly filled by the .50 caliber Browning Colt repurposed the T4 to fill an anti-armour role, which the .50 caliber M2 had originally been designed for twenty years earlier. The T4 was outfitted with a 2x power telescopic sight mounted on top of the receiver, which considering the weapon’s probable recoil - even with its large recoil spring, may have been at best little use and at worst a danger to the operator. According to the original caption of image #2 the T4 was allegedly capable of an impressive 800 rounds per minute, a significant increase from the rates of fire listed for the earlier T-variants. The original notes on the reverse of the photograph also described the gun as having “right or left hand feed” from a side mounted loading tray which fed from either 10-round clips or a flexible belt of the large proprietary .90 caliber rounds
The T4, like its cousins, was never adopted and by 1941 the average thickness of European tank armour had increased to the point where the T4 would have proved ineffective against German armour such as the Panzer IV, although it may have proved effective against thinner Japanese armour in the Pacific. It is unclear if Colt got to the stage of testing the weapon against armour and sadly there is little information on the performance of the T4.
Image One Source
Image Two Source
The Experimental US Cal. 90 Series Cannon, A.G. Williams, (2013) (source)
The Machine Gun: History, Evolution, and Development of Manual, Automatic, and Airborne Repeating Weapons, G. M. Chinn, (1951) (source)
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