It was developed as a simpler, less costly replacement for the renowned Thompson 1928 "Tommy Gun". It uses the same .45 ACP cartridge and has a firing rate of 600-700 rpm. It was widely used by American military Sergeants in World War II and adopted by the Empire Bay Police Department for use against the gangster presence in the city.
The weapon has a magazine capacity of 30 rounds and the player can carry an additional 3 magazines for a total of 120 rounds. It has a fully automatic rate of fire with less recoil than the Thompson 1928, making it more accurate with better range. It occupies a slot in the top of the weapons HUD along with other automatic weapons.
- May be carried by police officers when wanted level reaches 4 stars.
- May be carried by enemy gangsters in Chapters 9, 12, 14, and 15.
- In Joe's Adventures, one will be dropped by a detective at the Yacht Club in Witness - Frozen Memories. However, the only source of ammunition for the weapon is killing police officers at a 4 star wanted level or replaying Witness - Frozen Memories.
- In The Betrayal of Jimmy and Jimmy's Vendetta they may be dropped by enemy as the player progresses through the DLC.
- You can find more real world information about the Thompson M1A1 on its Wikipedia page.
- It can be seen in Chapter 1, where it is used by one of the paratroopers, fighting the Germans.
- A similar weapon, the Trench 1938, appears in Mafia III.