Thompson Autorifle

Thompson Autorifle Model 1923 (top) and SMG Model 1921

The Thompson Autorifle was a semi-automatic rifle that used a Blish Lock to delay the action of the weapon. It was chambered in .30-06, with the 1923 model in 7.62×54mmR Russian rifle rounds.

Several prototypes of the Autorifle were submitted by Auto-Ordnance to the military for the semi-automatic rifle trials, but it was not adopted. The Autorifle Model 1929, in .276 Pedersen, was tested in a competition with the rifles by J.D. Pedersen (delayed blowback) and John C. Garand (gas-operated), which culminated in the adoption of the M1 Garand.

On the positive side, the Autorifle action avoided the complexity of recoil-operated and gas-operated actions. On the negative side, the Autorifle required lubricated ammunition for proper functioning and the ejection of spent cartridge casings was so violent as to be hazardous to bystanders.^[1]

Function

For reloading, the Thompson Autorifle uses an interrupted screw delayed blowback operation where the bolt has 85° angled interrupted rear locking lugs that have to overcome a rotation of 110° ( 90° to unlock before the angle blend of 70°/40° and 6°) that delays the action until the gas pressure drops to a safe level to eject. The bolt cocks the striker on opening (a la Mauser) and fires from a closed position. When firing the trigger when pulled pushes a lever connected to a sear to fire the weapon. The receiver is of a round section with the safety switch at the rear along with the rear sight. The magazine is stripper fed holding 5 rounds and lubricated by oiled pads, later prototypes used 20 round M1918 BAR magazines.^[2]

References

• Experimental Semiautomatic Rifles 1919-31

1. ↑ Julian S. Hatcher, Hatcher's Notebook, MSPC 1947, pp.44-46, 155-156, 165-166.
2. ↑ Tracie L. Hill, Thompson: The American Legend 1996 by Collector Grade Publications Inc. Cobourg, Ontario Canada, ISBN 0-88935-208-9, pp.6-14, 31-36.