ArmaLite AR-18

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ArmaLite AR-18
The ArmaLite AR-18
Type Assault rifle
Place of origin United States
Service history
Used by See Users
Production history
Designer Eugene Stoner (AR-16)
Arthur Miller
Designed 1963
Manufacturer ArmaLite (U.S.)
HOWA Machinery Co. (Japan)
Sterling Armaments Company. (UK)
Produced 1963–1980
Variants AR-18K
Foreign derivatives based upon the AR-18 include the British SAR-87, Singaporean SAR-80 and the Japanese Howa Type 89
Bullpup adaptations include Australian Bushmaster M17S
Weight 6.7 lb (3.0 kg) (empty)
7.18 lb (3.3 kg) (loaded w/20 rd. magazine)
Length 38 in (970 mm)
Barrel length 18.25 in (464 mm) (6-groove rifling)

Cartridge 5.56x45mm NATO
Action Short-stroke piston, rotating bolt
Rate of fire 750 rounds/min
Muzzle velocity 3,250 ft/s (991 m/s)
Feed system 20, 30, or 40-round box magazine
Sights Iron or removable 3× scope

The AR-18 is a gas operated, selective fire assault rifle chambered for 5.56x45mm ammunition. The AR-18 was designed at ArmaLite in California by Arthur Miller, George Sullivan, and Charles Dorchester in 1963 as an improved alternative to the AR-15 design, which had just been selected by the U.S. military as the M16. While the AR-18 was never adopted as the standard service rifle of any nation, its production licence was sold to companies in Japan and England, and it is said to have influenced many later weapons such as the British SA80,[1] the Singaporean SAR-80 and SR-88, the Austrian Steyr AUG, and the Heckler and Koch G36. It gained some notoriety through its use by the Provisional IRA, which allegedly christened it the "Widowmaker".[2]


Soon after the adoption of the 7.62x51mm NATO M14 rifle in 1957, the U.S. Army's Continental Army Command (CONARC) began an investigation of Small Caliber High Velocity (SCHV) rifles as an off-shoot of the military's existing research program, Project SALVO. ArmaLite and Winchester Arms were solicited by CONARC to provide prototype automatic rifles chambered for high velocity centerfire .22 rounds. ArmaLite's AR-15 was a scaled down version of the 7.62mm AR-10, which had appeared too late to be a serious contender against the M14 for adoption by the US Army. Its competitor was the Winchester .224 Light Rifle,[3] a 'Carbine' Williams prototype carbine design in a .22 high velocity round which was similar to, but not interchangeable with, the .223 Remington (5.56x45mm). During the protracted U.S. military trials of the AR-15, ArmaLite's corporate owners Fairchild essentially gave up on the design, and sold the AR-15 production rights to Colt. Fairchild also spun off ArmaLite as an independent company, allowing the new owners to buy all of the company's designs except for the AR-10 and AR-15. When the U.S. military ultimately selected the AR-15 as the M16, ArmaLite could no longer profit from its adoption.

The Armalite AR-16 appeared in the later 1950s. The AR-16, a 7.62mm NATO selective-fire rifle, was Eugene Stoner's final design for ArmaLite. The AR-16 and its predecessor, the AR-12 were designed by Stoner in response to demands by the military forces of smaller, less developed nations for a less expensive, yet state-of-the-art selective-fire military rifle that unlike the AR-10 and AR-15, could be produced inexpensively of heavy-gauge sheet metal using automatic screw machines, lathes, and presses.[4][5] The AR-12 originally featured a direct-impingement (DI) gas operation system, but this was changed to a more conventional short-stroke gas piston in the AR-16 after ArmaLite sold the production rights to the DI system to Colt Firearms.[4] The AR-16 had a short, 15-inch barrel, hinged wooden butt, and weighed 8.75 pounds empty; only three examples were built.[5] Eugene Stoner left ArmaLite in 1961, shortly before Fairchild divested itself of ownership.[6]

The U.S. military's later adoption of the AR-15 gave legitimacy to its 5.56mm cartridge, and ArmaLite sought to develop a competing design chambered in 5.56mm that did not infringe on the Colt licence agreement. With Stoner gone, it was decided to scale down the AR-16, and ArmaLite's new chief designer, Arthur Miller, embarked on the project. The resulting 5.56mm design appeared in 1963 and was named the AR-18. Miller later received U.S. Patent 3,246,567 for the rifle in 1969.

Construction and design[edit]

Overall, the new AR-18 rifle was much more conventional than previous ArmaLite designs, although it used the relatively new stamped steel construction from its predecessor, the AR-16. Despite being pioneered by the Germans during WW2 in weapons such as the MP44, and later adopted for the Soviet AKM, the use of stamped and welded sheet metal components was still uncommon in the manufacture of military rifles in the West in the early 1960s, which had, until then, largely retained the use of traditional machined forgings.[7] Compared to the smooth lines of the AR-15, the AR-18 faced criticism over its stamped and welded construction, which had demonstrably greater tolerances in parts fit.[8][9] However, the rifle proved to be both reliable and very accurate at all ranges up to 460 metres (500 yards). Its simple construction promised significantly reduced production costs, and allowed it to be licence-produced locally on less advanced machinery, potentially reducing dependence on foreign manufacturers.[7] Moreover, the gas piston operation of the AR-18 proved much more resistant to carbon fouling than the direct gas impingement system of the earlier AR-10 and AR-15 rifles, as it did not vent gas and carbon particles directly into the receiver.[10]

The AR-18's action was powered by a short-stroke gas piston above the barrel. The gas piston was of 3-piece design to facilitate disassembly, with a hollow forward section with 4 radial gas vent holes fitting around a stainless steel gas block projecting rearwards from the foresight housing. The gas was vented from the barrel and travelled via a vent through the foresight housing into the hollow front section of the piston, which caused it to move rearwards a short distance. The rear end of the piston emerged through the barrel extension to contact the forward face of the bolt carrier, causing it in turn to move rearwards. The bolt itself was of similar configuration to the AR-15 with 7 radial locking lugs engaging corresponding recesses in the barrel extension, and the extractor in place of the 8th lug. The bolt was moved into and out of the locked position via a cam pin that engaged a helical slot in the bolt carrier, which rode on two metal guide rods (each with its own return spring) instead of contacting the receiver walls, providing additional clearance for foreign matter entering the receiver.[11] Unlike the AR-15, the cocking handle fitted directly into a recess in the bolt carrier and reciprocated with it during firing, allowing the firer to force the breech closed or open if necessary. The cocking handle slot had a spring-loaded cover that could be closed by the user to prevent debris entering the receiver, and it would open automatically as the bolt carrier moved rearwards after the first shot. The recoil springs were housed within the receiver, differing from the AR-15 which housed its more elaborate buffer mechanism in the buttstock. The AR-18's compact design enabled the use of a side-folding stock with a hinging mechanism (that later proved to be less than adequately rigid).[9]

The sights were of similar design and sight picture to those of the AR-15 - a 2-position flip aperture rear sight and post foresight - but the rear sight was made of stampings. A notable change is the use of a more conventional lower sight line closer to the axis of the bore, in contrast to the elevated sights of the AR-15. A dovetail was spot welded to the receiver in front of the rear sight for a proprietary ArmaLite quick-detachable scope mount.

Overall, the design is simple and effective with some clever touches; for example the bolt guide rod assembly guides the bolt in the receiver, retains the recoil springs and the rear end of the top handguard, as well as serving as the latch holding the upper and lower receivers together in the closed position. Disassembly is somewhat similar to the AR-15, with the working parts accessed by the rifle pivoting open on a cross-pin immediately forward of the magazine well.

Production and operational use[edit]

A Sterling Armaments AR-180 on display at the National Firearms Museum.

The AR-18 was put into limited production at ArmaLite's machine shop and offices in Costa Mesa, California. A semi-automatic version of the AR-18 known as the AR-180 was later produced for the civilian market between 1969 and 1972. ArmaLite was never equipped to build small arms on a production basis, and the Costa Mesa AR-18 and AR-180 rifles frequently show evidence of hand-fitting. A production license was granted to Nederlandsche Wapen-en Munitiefabriek (NWM) of Den Bosch, the Netherlands, but it is doubtful that any AR-18 rifles were actually produced there.[7] A license to produce the AR-18/180 was then sold to Howa Machinery Co., of Japan, and the rifle was produced there from 1970 until 1974, when new controls on export of military arms by the Japanese government forced the company to cease all small arms production.[7] From 1975 until 1983, the Sterling Armaments Company of Dagenham, Essex, in the United Kingdom produced the AR-18/AR-180.[5][7]

Unlike the AR-15/M16, the AR-18 did not see substantial sales success, and was never officially adopted by any country as their standard service rifle. The reasons for this are unclear, but may have had something to do with the existing sales popularity of the AR-15/M-16, as well as the need for additional field testing and evaluation of the Costa Mesa-produced rifles, which were still in the advanced prototype stage. The AR-18 was purchased for evaluation trials by various armed forces, including the United States (1964) and the United Kingdom (1966).[1] These suffered various malfunctions during evaluation trials by various nations.[5] During the US trials at Aberdeen Proving Grounds in 1964, the AR-18's functioning was found to vary from lot to lot of ammunition.[12] The evaluating board concluded that while the basic design of the AR-18 was sound, it required additional minor revisions and changes to improve safety and reliability before it could be considered for adoption as a service rifle.[12] The British Ministry of Defence (MOD) tested the AR-18 in March 1966, and found the design unsatisfactory in performance during mud and sand trials. ArmaLite made several minor production modifications to the design commencing in 1965, and the U.S. Army was directed to re-evaluate the AR-18 at the end of 1969. Testing was conducted at Aberdeen Proving Grounds, conducted by arsenal employees and the Infantry Board at Fort Benning, Georgia. However, American procurement officials were not interested in acquiring yet another 5.56 mm service rifle.[5] Instead, the AR-180 was sold on the civilian market, while the AR-18 sold in small quantities to police and law enforcement organizations, as well as armies and security forces of nations such as Botswana, Haiti, and Swaziland. Still others found their way into the hands of terrorist or paramilitary groups, such as the Provisional IRA in Northern Ireland.[13] In 1968, dissatisfied with efforts to market the AR-18, Arthur Miller left ArmaLite.


The standard AR-18 versions manufactured by ArmaLite, Howa and Sterling differ only in minor details. Rifles were normally equipped with sling, cleaning kit (bore/brush), and a knife-type bayonet with scabbard. An optional bipod with case was available.

The AR-180 was capable of semi-automatic fire only and was externally identical in appearance to the AR-18 with one exception; the selector had only 2 positions, omitting the third "AUTO" position found on the AR-18.

Sterling manufactured a small number of sporter variants called the AR-180 SCS, of which only 385 were reputed to have been made.[14] It had a large single-piece wooden thumbhole stock that replaced the butt, pistol grip and handguard of conventional versions. The metal parts differ in the lack of the ejection port cover, a PH prefix to the serial number and adapted safety and magazine release controls.

Sterling also manufactured small numbers of a short version, the AR-18S.[2] This version used the same basic mechanism and folding butt, but had a 257 mm (10.1 in) barrel and a length of 765 mm (30.1 in) with the butt extended. The shortened barrel was fitted with a cone-shaped flash suppressor to address the additional muzzle flash resulting from the short barrel. Some examples had an additional pistol grip fitted to the underside of the handguard.

A 2.75 X 20 mm telescopic sight was available but few were sold.[2] It was marked "ArmaLite", and had a quick-detachable, see-through mount that attached to an integral dovetail spot-welded to the top of the receiver.

Also of note is that bullpup conversions of the AR-18 and the Stoner 63 were fabricated by Enfield, the rival company of Sterling Armaments Ltd when developing the SA80.[15][16][17]

Recent developments[edit]

The ArmaLite brand was purchased in 1996 by Eagle Arms, a small U.S. arms manufacturer, who adopted the ArmaLite brand for their company. An updated model of the AR-180 was introduced in 2001 as the AR-180B, with a molded polymer lower receiver replacing the stamped steel original. The new lower receiver is combined with the buttstock, which is fixed on the AR-180B, instead of the side-folding butt on the original AR-18 and AR-180. Other AR-180B changes include the use of standard AR-15 trigger group and rear sight parts, a straight cocking handle replacing the earlier cranked style and the deletion of the original AR-18/180 spring-loaded dust cover for the cocking handle slot.[18] The AR-15 magazine release is also used, in contrast to the original AR-18 which had a different magazine release and corresponding slot in the body of the magazine, meaning AR-15 magazines needed a new slot cut to fit properly in the AR-18. As a result the AR-180B uses standard AR-15/M16 magazines. An AR-180B version with a Picatinny rail was planned for production, however before it appeared AR-180B production was put on hold due to sluggish sales and other production priorities, along with the fact that the polymer lower receiver is no longer produced.



  1. ^ a b "A Historical Review of Armalite, page 5". ArmaLite, Inc. January 4, 2010. Retrieved June 2, 2011. 
  2. ^ a b c "ArmaLite AR-18: The Widowmaker". Retrieved June 2, 2011. 
  3. ^
  4. ^ a b Smith, W.H.B. and Smith, Joseph E. (ed.) Small Arms of the World, 9th ed., Harrisburg, PA: The Stackpole Company, ISBN 978-0-81171-566-9 (1969), p. 656
  5. ^ a b c d e Walter, John, Rifles of the World, Iola, WI: Krause Publications, ISBN 978-0-89689-241-5 (2006), p. 42
  6. ^ Pikula, Sam (Major), The ArmaLite AR-10, Regnum Fund Press (1998), ISBN 9986-494-38-9, p. 92
  7. ^ a b c d e Hogg, Ian and Weeks, John, Military Small Arms of the Twentieth Century, 6th ed., Northfield, IL: Digest Books Inc., ISBN 0-87349-120-3 (1991), p. 181
  8. ^ Dolazell, Harry, ArmaLite/Sterling AR-18 5.56mm Rifle, Colchester, Essex (UK): GunMart Magazine, Aceville Magazines Ltd. (2000)
  9. ^ a b Cutshaw, Charles, Return of the AR-180, Guns Magazine, Vol. 49, No. 6 (June 2003): In addition to an occasional wobbly stock, the upper receiver on some AR-18 rifles can be rocked up and down against the lower.
  10. ^ "A Historical Review of Armalite, page 13". ArmaLite, Inc. January 4, 2010. Retrieved June 2, 2011. 
  11. ^
  12. ^ a b Ballistic Research Laboratory, Aberdeen Proving Ground, A Kinematic Evaluation of the AR-18 Rifle, Cal. 0.223, Philadelphia, PA: Frankford Arsenal (undated)(unclassified)
  13. ^ a b Bishop, Chris. Guns in Combat. Chartwell Books, Inc (1998). ISBN 0-7858-0844-2.
  14. ^ "ArmaLite Sterling AR180 SCS .223 Thumbhole Target Stock". Archived from the original on 11 July 2011. Retrieved June 2, 2011. 
  15. ^
  16. ^
  17. ^
  18. ^ "ArmaLite, Inc. AR-180B Rifle". Archived from the original on 7 June 2011. Retrieved June 2, 2011. 

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