The Auto-Ordnance Thompson M1SB is the simplified M1 military variant of the Thompson, featuring a straight blowback action without the complex Blish lock of the 1928 commercial model, a simplified stick magazine, and M1 horizontal foregrip. The M1 configuration is the most common WWII Thompson pattern. Type: Carbine Action: Semi-Automatic Caliber: .45 ACP Capacity: 30 Year introduced: 1986, USA Weight: 10.8 oz Overall length: 38" Status: Active Intended use: Historical Recreation, Collecting