While the US Army was satisfied with the Thompson as a fighting weapon in World War Two, it was most certainly not happy with the gun's exorbitant price tag. The Thompson was a very expensive gun, and the Army wanted to see that change. In March of 1942, engineers at the Savage factory submitted a simplified version for Army consideration, and it was accepted and adopted the very next month. Savage would transition from M1928A1 production to the new M1 pattern in June and July of 1942.

This new M1 Thompson had eliminated at last the unique and unnecessary Blish lock system in favor of a simple blowback action delayed only by bolt mass. In addition to greatly simplifying the production of bolt components, this also allowed the receiver internal shape to be much simplified. A further simplification would follow shortly, as the hammer and floating firing pin were replaced by a fixed firing pin milled into the bolt face in October of 1942 - this new type being designated the M1A1. Another 715,000 M1 and M1A1 Thompsons would be produced by Savage and Auto-Ordnance by February of 1944, when the Thompson was finally replaced by the yet cheaper M3 "Grease Gun".

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

Note: I refer to the M1A1 in this video as a transferrable gun; it is actually a pre-May dealer sample. Sorry!