The first production M1 was successfully proof fired, function fired, and fired for accuracy on July 21, 1937. Thus began manufacture of what was to become the greatest production effort in the history of Springfield Armory. During the entire production history of the M1 rifle, Springfield Armory produced over 4.5 million M1s.
General Douglas MacArthur reported on the M1 to the Ordnance Department during heavy fighting on Bataan that: "Under combat conditions it operated with no mechanical defects and when used in foxholes did not develop stoppages from dust or dirt. It has been in almost constant action for as much as a week without cleaning or lubrication."
General George S. Patton Jr. reported to the Ordnance Department on January 26, 1945: "In my opinion, the M1 Rifle is the greatest battle implement ever devised."
The M1 rifle was described in military manuals as "a gas-operated, clip-fed, air-cooled, semi-automatic shoulder weapon." The design incorporated a spring-loaded piston operating within a gas cylinder mounted on the end of the barrel. Gas was fed through a gas port in the barrel to a fixture mounted at the muzzle of the barrel. As the bullet passed this point, exiting the barrel, the compressed gas behind it flowed down a port to the piston. The piston drove a 16-inch operating rod to the rear where a cam on the back of the operating rod unlocked a two lug rotary bolt and then carried the bolt to the rear of the receiver. The operating rod, a hollow tube, contained a spring which resisted rearward movement. The spring, in turn, exerted pressure on the follower rod which operated the feeding mechanism of the weapon. Upon firing of the last cartridge, the clip was automatically ejected.