Auto-Ordnance Corporation

Auto-Ordnance was a U.S. arms development firm founded by retired Colonel John T. Thompson of the United States Army Ordnance Department in 1916.

The engineers learned that the Blish lock design, which was a delayed blowback action, was ineffective with the .30-06 rifle cartridge but very effective with the .45 ACP pistol round.

The Thompson M1A1 was typically issued to tankers and others affiliated with vehicles, due to the weapon's heavy weight and short effective range.

Numrich Arms Auto-Ordnance assembled limited numbers of Thompson submachine guns primarily for law enforcement from existing receivers found in the crates purchased in 1951, including M1928A1 and M1A1 models.

Dimensional changes prevent installation of full-auto bolts and fire control groups in the semi-auto frames or receivers.