The ArmaLite AR-10 is a 7.62×51mm NATO battle rifle designed by Eugene Stoner in the late 1950s and manufactured by ArmaLite (then a division of the Fairchild Aircraft Corporation). When first introduced in 1956, the AR-10 used an innovative combination of a straight-line barrel/stock design with phenolic composite, a new patent filed gas-operated bolt and carrier system and forged alloy parts resulting in a small arm significantly easier to control in automatic fire and over 1 lb (0.45 kg) lighter than other infantry rifles of the day. Over its production life, the original AR-10 was built in relatively small numbers, with fewer than 10,000 rifles assembled. However, the ArmaLite AR-10 would become the progenitor for a wide range of firearms.

In 1957, the basic AR-10 design was rescaled and substantially modified by ArmaLite to accommodate the .223 Remington cartridge, and given the designation ArmaLite AR-15

In 1959, ArmaLite sold its rights to the AR-10 and AR-15 to Colt’s Manufacturing Company due to financial difficulties, and limitations in terms of manpower and production capacity.[3] After modifications (most notably, the charging handle was re-located from under the carrying handle like AR-10 to the rear of the receiver), the new redesigned rifle (the AR-15) was subsequently adopted by the U.S. military as the M16 rifle. Colt continued to use the AR-15 trademark for its line of semi-automatic-only rifles, which it marketed to civilian and law-enforcement customers as the Colt AR-15.