The Auto-Ordnance Thompson M1SB in .45 ACP with 16.5-inch barrel is the semi-auto M1 variant of the Thompson, featuring the simplified M1 WWII-era straight blowback action without the bronze oscillator and actuator of the 1928 model. More reliable and simpler to maintain than the 1927A-1, it accepts stick magazines and is the recommended configuration for shooters who plan to fire regularly. Type: Semi-Auto Rifle Action: Blowback Caliber: .45 ACP Capacity: 30 Year introduced: 1976, USA Weight: 10.5 oz Overall length: 41" Status: Active Intended use: Collecting, Plinking, Home Defense