The USMC had acquired a few hundred early 1921 model Thompson submachine guns in 1926, and prompted the US Navy to formally test the guns. The Navy requested a reduction in the rate of fire, in order to improve controllability and reduce ammunition consumption (20 round magazines go quickly at 900rpm!). Auto-Ordnance happily complied, and Oscar Payne returned to the company on his spare time to modify the gun. He did this my adding a substantial amount of mass to the actuator, and was able to reduce the rate of fire substantially. The Navy subsequently ordered 500 guns, designated the Model of 1928.

Since most of the original 15,000 guns made by Colt were still in inventory, Auto-Ordnance simply overstamped the "1" at the end of "1921" with an "8" and put the new heavier bolt assemblies in the guns, leading to the collector term "21/28 overstamp" for these Thompsons. The lower rate of fire would become the new standard for the Thompson.

By late 1928, only about 6,000 Thompsons had been sold, and by the end of 1938 10,300 had been sold. Of these, about 1500 total had gone to the US government, about 4100 exported, and the remainder to American police and security agencies. Times were not good for the Thompson - it was an expensive military weapon without a war that needed it. Despite the gun's huge notoriety, it was actually not used in particularly large numbers by the motor bandits of the 20s and 30s, nor in great numbers by the police. While the FBI did purchase Thompsons, they only bought 115 in total, and not until 1935.

This is the second part in a 5-part series on the development of the Thompson...