By 1940 many European Nations were clamouring for Tommy guns and large-scale production commenced for France, UK and Yugoslavia. All the orders went to the UK for use by commandos and jungle warfare. When the USA entered the Second World War the army wanted a submachine gun in large numbers. This meant redesigning the Thompson to make it more simple with a straightforward blow-back action, a fixed rearsight and no compensator. Despite such changes the Thompson was still machined, heavy and not easy to strip or maintain. This did not stop it becoming a favourite with the US Armed Forces. Calibre 0.45 in. Magazine - box only, 20 or 30 rounds. Weight 10.45 lb. Rate of fire 700 RPM.
Marks and Stamps: (L side of receiver) THOMPSON SUBMACHINE GUN CALIBER .45 M1A1 No. 333250 (R side of receiver) AUTO-ORDNANCE CORPORATION BRIDGEPORT,CONNECTICUT,U.S.A. (Stock) A A U| Accession Number: 162 | Period of Use: 1942 - present |
| Type: Machine pistol/SMG | War Zones: Second World War; Malaya; Korea; Suez; Indo-China |
| Country of Origin: USA | Type Date: 1942 |
| Manufacturer: Auto-Ordnance Corporation, Bridgeport Conn. | Serial Number: 333250 |
| Manufacture Date: Unknown | Calibre/Ammunition: 0.45" ACP |
| Weight: 4820g | Length Overall: 813mm |
| Cyclic Rate: 700rpm | Length Barrel: 266mm |
| Deactivation Certificate Number: DA 5541 |