The Thompson Autorifle was a semi automatic rifle that used a rotating Blish Lock to delay the action. 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 and Colt to the military for the semi-automatic rifle trials at Springfield Armory, 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, otherwise ejection of spent cartridges was so volatile that it was deemed hazardous to bystanders; casings were ejected with enough force to get stuck in wooden doors a few feet away.
The Thompson Autorifle is a semi automatic rifle chambered in the .30 06 round. It uses a 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.