AR10

ArmaLite was incorporated on 1 October 1954 as a subdivision of the Fairchild Engine and Airplane Corporation, founded by George Sullivan and intended to develop small arms concepts for licensing rather than to manufacture them. Eugene Stoner, hired as chief design engineer, produced the first AR-10 prototypes between 1955 and early 1956. ArmaLite entered the rifle late into the United States Army trials to replace the M1 Garand, submitting two hand-built rifles to Springfield Armory in the autumn of 1956 against Springfield's T44 and the FN FAL. An experimental aluminium/steel composite barrel, specified by Sullivan over Stoner's objections, burst during a torture test in early 1957; the Armory's final report advised against adoption, and the Army selected the T44, which entered production as the M14. On 4 July 1957 Fairchild ArmaLite sold a five-year manufacturing licence to the Dutch firm Artillerie Inrichtingen. The same year the design was rescaled for the .223 Remington cartridge as the AR-15. ArmaLite sold its rights to both rifles to Colt's Manufacturing Company in 1959.

The AR-10 is an air-cooled, magazine-fed, gas-operated rifle using a piston formed within the bolt carrier and a rotating bolt. Rather than a separate gas cylinder, piston and operating rod, propellant gas travels from a port near the middle of the barrel through a steel tube into a chamber between the rear of the bolt and the interior of the bolt carrier, the bolt being fitted with piston rings; excess gas vents through ports in the carrier once it has moved rearward. The bolt locks into a barrel extension rather than the receiver, permitting a forged and machined aluminium receiver. The stock is a fibreglass-reinforced phenolic composite over a rigid plastic foam core, with fibreglass-reinforced handguards and pistol grip. The straight-line stock reduces muzzle climb in automatic fire and required elevated sights, the rear sight and elevation wheel being housed in a carrying handle that also shrouded the cocking lever. The hinged receiver derives from the FAL, the ejection port cover from the StG44, and the bolt locking arrangement from the M1941 Johnson rifle. All AR-10s used Stoner's aluminium "waffle" magazine.

Artillerie Inrichtingen production is divided into the Sudanese, Transitional and Portuguese models. Sudan took delivery in October 1958; its rifles carried Arabic sight graduations and remained with Sudanese Special Forces until 1985. West Germany purchased 135 rifles in 1958. Cuba, Guatemala, Italy, Myanmar, Nicaragua, Portugal, Romania, Finland and the Dominican Republic were among other purchasers, the Italian Navy issuing the rifle to its COMSUBIN commandos. The Portuguese model introduced a heavier chrome-lined-chamber barrel, wider bolt lugs, a strengthened extractor, a three-position gas regulator and a cocking handle with forward bolt assist; some 4,000–5,000 were sold to Portugal through SIDEM International in 1960 and issued to the Caçadores paraquedistas, who used them in Angola and Mozambique and as late as 1975 in Portuguese Timor, some fitted with telescopic sights or metal buttstocks for grenade launching. A carbine was built for KLM Arctic survival kits, and a belt-fed AR-10 LMG remained experimental. A.I. ceased production in 1960. ArmaLite Inc., under Mark Westrom, introduced the semi-automatic AR-10B in 1995, based on the AR-15A2, followed by the AR-10A in 2012.