How a M14 works

The M14 rifle, officially the United States Rifle, 7.62 mm, M14, is an American automatic rifle that fires 7.62×51mm NATO (.308 in) ammunition. It became the standard-issued rifle for the U.S. military in 1959 replacing the M1 Garand rifle in the U.S. Army by 1961 and the U.S. Marine Corps by 1965 until being replaced by the M16 rifle beginning in 1964. The M14 was used by U.S. Army, Navy, and Marine Corps for basic and advanced individual training (AIT) from the mid-1960s to the early 1970s.

The M14 was the last American battle rifle issued in quantity to U.S. military personnel. It was replaced by the M16 assault rifle, a lighter weapon using a smaller caliber intermediate cartridge. The M14 rifle remains in limited service in all branches of the U.S. military as an accurized competition weapon, a ceremonial weapon by honor guards, color guards, drill teams and ceremonial guards, and sniper rifle/designated marksman rifle. Civilians models in semi-automatic are used for hunting, plinking, target shooting, and shooting competitions.

The M14 is the basis for the M21 and M25 sniper rifles which were largely replaced by the M24 Sniper Weapon System. A new variant of the M14, the Mk 14 Enhanced Battle Rifle has been in service since 2002.

The M14 was developed from a long line of experimental weapons based upon the M1 Garand rifle. Although the M1 was among the most advanced infantry rifles of the late 1930s, it was not an ideal weapon. Modifications were already beginning to be made to the basic M1 rifle's design during the last months of World War II. Changes included adding fully automatic firing capability and replacing the eight-round en bloc clips with a detachable box magazine holding 20 rounds. Winchester, Remington, and Springfield Armory's own John Garand offered different conversions. Garand's design, the T20, was the most popular, and T20 prototypes served as the basis for a number of Springfield test rifles from 1945 through the early 1950s.