Military-specification 1911A1 with arched mainspring housing and 5-inch barrel. Type: Pistol Action: Semi-Automatic Caliber: .45 ACP Capacity: 7 Year introduced: 1924, USA Weight: 39 oz Overall length: 8.5" Status: Discontinued Military use: Yes Intended use: 1911A1 modifications included arched housing and shorter trigger over original 1911.