This weapon, designed by John T. Thompson, was the original 'gangster gun' (and had nicknames such as the 'Chicago Typewriter' and 'The Chopper'), rising to fame during the 'Roaring' Twenties and used by such notables as Al Capone and John Dillinger. Originally it operated a form of blowback system, fired the .45 ACP cartridge and had a 50- or 100-round drum magazine but was modified over the course of its life. While one of the first firearms in Auxiliary Unit service, over time, many were replaced by the Sten Gun.
The Second World War bred a huge number of sub-machinegun designs, including the Russian PPSh-41 and PPS-43, the American Reising Models 50 and 55, the Japanese Type 100, the French MAS Model 1938, the Australian Owen and Austen Guns and the ubiquitous British Sten Gun. Many of these, including the Thompson, saw combat not only in the Second World War, but in the wars of the Cold War era, including the Chinese Civil War, Korea, Indochina, Vietnam, the Arab-Israeli Wars, and Indonesia. It has also been used in a variety of conflicts since the end of the Cold War, including the war in the former Yugoslavia.
Specification (M1):
Calibre: .45 ACP
Length: 813mm (32in)
Length of Barrel: 267mm (10.5in)
Weight Loaded: 4.74kg (10.45lbs)
Magazine: 20 or 30-round box
Rate of Fire: 700rpm
Muzzle Velocity: 280mps (920fps)
You can find out more about the "Tommy gun" in these CART articles: Overview, History and Factsheet