The Operator series of pistols is a range of customized M1911A1s built by Springfield Armory and chambered in .45 ACP. Springfield Armory is one of several companies that were contracted to build government-issue M1911s and M1911A1s during and after the World Wars. The current Springfield Armory that makes the Operators and produces several customized versions of the venerable handgun for military and civilian use is a commercial company that purchased the Springfield Armory name in 1974.