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Title:	GUN, AUTOMATIC -  U.S. GUN T31 AIRCRAFT 20MM SN# 5885
Maker/Manufacturer:	OLDSMOBILE
Date of Manufacture:	1944
Eminent Figure:
Catalog Number:	SPAR 7811
Measurements:	OL:198CM 78" BL: 52.5" 99.5 lbs.

Object Description:

U.S. GUN T31 AIRCRAFT 20MM SN# 5885
Manufactured by Oldsmobile Division of GM - The 20mm T31 is a combination blowback and gas-operated aircraft weapon. The gun is air-cooled and has a cyclic rate of fire of 750 to 850 rounds per minute. It is designed for mounting as a fixed gun in the wing or fuselage of an airplane. It may also be mounted as flexible gun in a turret. The gun is also designed to be synchronized to fire between the propeller blades of an airplane. The gun may be fired from the left or right sides. 9-groove rifling, right hand twist. Rate of fire 750 to 850 rpm. Muzzle velocity 2840 fps. Weapon weighs approximately 99.5 lbs. Flash hider and internal parts missing.

Markings:
Receiver: GUN AUTOMATIC/20MM T31/NO. 5885/ORD. DEPT. U.S.A./ABO OLDSMOBILE/1944 U.S. INSP.
Barrel: TUBE NO. 7280/OLDSMOBILE.

Weapon donated to Springfield Armory Museum, Inc. by Olin-Corporation (Winchester-Western) on 14 March 1973.

Notes: "Gun, Automatic, 20-mm T31. This is an automatic blowback and gas-operated aircraft weapon. The basic difference between the 20-mm AN-M2 and the 20-mm T31 is that the T-31 is a light-weight high-speed gun having the recoil system and the cradle built into the gun, whereas the AN-M2 gun uses the Edgewater adapter, and the mount is a part of the airplane to which the gun is attached. The basic concept of the cradle and recoil system came from Oldsmobile and design and development of the weapon was done at Oldsmobile. The T31 gun complete with feeder, cradle, recoil system, and solenoid weighs 116 pounds while the AN-M2 basic gun without mounts or solenoid weighs 115 pounds. The T31 gun has an overall length of 77.75 inches and the AN-M2 is 92.8 inches overall. The rate of fire of the T31 is approximately 720 rounds per minute, while that of the AN-M2 is about 100 rounds per minute less. This gun was produced in quantity at Oldsmobile. The T31 combined features of the T26, T28 and T29. This project was supervised by Watervliet. T31 indicates the rear-seared gun. This was standardized as the M3." - Chinn

DISPOSITION OF T31s THAT WERE IN SPRINGFIELD ARMORY MUSEUM COLLECTION:
Army #5685 - U.S. GUN T31 SN# 5830 - Transferred to Patterson on 7 February 1984.
Army #7718 - U.S. GUN T31 SN# 15198 - Transferred to Patterson on 7 February 1984.

See Chinn, Vol. III, pg. 391.

References:
Chinn, George M. THE MACHINE GUN. Vol. III. Department of the Navy. Washington, D.C. 1953.

TM9-229 - 20MM AUTOMATIC GUN M3 (T31), 1 JUNE 1944.