ArmaLite AR-10

ArmaLite AR-10 is a 7.62×51mm NATO battle rifle designed by Eugene Stoner in the mid-1950s and originally manufactured by ArmaLite, then a division of the Fairchild Engine and Airplane Corporation. It is historically significant as the direct predecessor of the ArmaLite AR-15, which was later adopted by the U.S. military as the M16 rifle.

Development and Design

The AR-10 was designed by Eugene Stoner, who joined ArmaLite as chief design engineer in 1954 after being hired by company founder George Sullivan. The first prototypes of the 7.62mm AR-10 emerged between 1955 and early 1956. The rifle incorporated several innovative features for its era: a straight-line barrel and stock design to reduce muzzle climb, a receiver made from forged and machined aluminum alloy, and furniture (stock, handguards, pistol grip) made from fiberglass-reinforced phenolic composite. These materials, borrowed from the aircraft industry, resulted in a rifle weighing approximately 6.85 lb (3.11 kg) empty—over 1 lb lighter than competing infantry rifles of the day.

The AR-10 used a gas-operated action with a rotating bolt. Stoner's gas system, patented as U.S. Patent 2,951,424, routed combustion gases from a port in the barrel through a steel tube back into the receiver, where they entered a chamber inside the bolt carrier. The bolt carrier acted as a movable cylinder and the bolt as a stationary piston, eliminating the need for a separate gas cylinder, piston, and actuating rod. The bolt locked into a steel barrel extension rather than the receiver itself, allowing the receiver to be made of lightweight aluminum. The rifle fed from 20-round detachable aluminum box magazines with pressed-in corrugations ("waffle" magazines).

U.S. Army Trials

In the fall of 1956, ArmaLite submitted two hand-built AR-10 rifles to the U.S. Army's Springfield Armory for testing as a potential replacement for the M1 Garand. The AR-10 competed against Springfield Armory's T44E4 (an updated M1 Garand in 7.62mm) and Fabrique Nationale's T48 (the FN FAL). Initial impressions from test staff were favorable, with some testers describing it as the best lightweight automatic rifle tested by the Armory.

However, during a torture test in early 1957, the rifle's aluminum/steel composite barrel—an untested prototype design insisted upon by ArmaLite president George Sullivan over Stoner's objections—burst after approximately 5,564 rounds. ArmaLite quickly replaced it with a conventional steel barrel, but the damage to the rifle's credibility was done. The final Springfield Armory report advised against adoption, stating it would take "five years or more to take it through tests to adoption." The Army selected the T44, which entered production as the M14 rifle in 1957.

Licensed Production and Variants

With the U.S. market closed, ArmaLite sold a five-year manufacturing license for the AR-10 to the Dutch arms manufacturer Artillerie-Inrichtingen (A.I.) on July 4, 1957. A.I. converted the design to metric dimensions and resolved manufacturing issues before commencing production. Firearms historians have identified three main A.I. production variants:

• Sudanese model (c. 1958): Lightweight fluted steel barrel, prong-style flash suppressor, fiberglass furniture, bayonet lug, sight graduations in Arabic. Approximately 2,500 rifles were sold to Sudan.
• Transitional model: Incremental improvements including removable plastic/metal handguards.
• Portuguese model (c. 1960): The most refined variant, with a heavier chrome-lined barrel, wider bolt lugs, stronger extractor, simplified three-position gas regulator, and a cocking handle with forward bolt assist. Approximately 4,000–5,000 were produced, nearly all sold to Portugal.

A small number of AR-10 carbines with 16-inch barrels were produced for KLM Royal Dutch Airlines as part of Arctic survival kits. Experimental variants included a 7.62×39mm version for Finnish and German evaluation and a belt-fed light machine gun prototype (AR-10 LMG), though the latter experienced persistent feed malfunctions and was never sold.

Service History

The AR-10 saw combat service primarily with Portuguese paratrooper battalions (Caçadores Páraquedistas) during Portugal's counter-insurgency campaigns in Angola and Mozambique from the 1960s into the 1970s. Portuguese forces found the rifle accurate and reliable under rugged field conditions. Some rifles were fitted with 3× or 3.6× telescopic sights for designated marksman roles. The AR-10's gas cutoff design allowed it to fire Energa rifle grenades without adjustment.

Sudanese AR-10s were used in clashes with guerrilla forces and remained in service with Sudanese Special Forces until 1985. Other purchasers included Guatemala, Burma (Myanmar), Italy, Cuba, and West Germany. The Cuban government under Fidel Castro acquired 100 Transitional model rifles originally ordered by the Batista regime, which were later transferred to Dominican revolutionaries.

Total production of the original AR-10 by both ArmaLite and A.I. amounted to fewer than 10,000 rifles. By 1960, hampered by Dutch export restrictions and lack of major sales, A.I. ceased AR-10 production. All parts inventories, tooling, and production records were sold or discarded.

Legacy

In 1957, the U.S. Army's Continental Army Command requested a lightweight .22-caliber selective-fire rifle. ArmaLite engineers Eugene Stoner, Jim Sullivan, and Bob Fremont scaled down the AR-10 design to produce the AR-15, chambered in .223 Remington (later 5.56×45mm NATO). In 1959, facing financial difficulties, ArmaLite sold the rights to both the AR-10 and AR-15 to Colt's Manufacturing Company for $75,000 plus a 4.5% royalty. After modifications—most notably relocating the charging handle from under the carrying handle to the rear of the receiver—the AR-15 was adopted by the U.S. military as the M16 rifle.

In 1995, the ArmaLite brand was purchased by Eagle Arms owner Mark Westrom, and the company introduced the AR-10B series, a semi-automatic-only rifle based on the AR-15A2 design scaled up for 7.62×51mm NATO. In 2012, ArmaLite introduced the AR-10A model, reverting to the original SR-25 pattern magazine. ArmaLite Inc. continues to produce AR-10 series rifles for civilian, law enforcement, and military markets.

Specifications (Original AR-10)