45, Automatic, M1911A1 in the Vietnam War era. The designation changed to Pistol, Caliber. 45, M1911 for the original model of 1911 or Automatic Pistol, Caliber. The pistol's formal designation as of 1940 was Automatic Pistol, Caliber. The M1911, also known as the Colt 1911, or the Colt Government, is a single-action, semi-automatic, magazine-fed, recoil-operated pistol chambered for the. 7-round or 8-round (.45 ACP) box magazine
