ArmaLite AR-18

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ArmaLite AR-18
The ArmaLite AR-18
Type Assault Rifle
Semi-automatic rifle
Place of origin United States
Service history
Used by See Users
Wars Communist insurgency in Malaysia
Lebanese Civil War
The Troubles
Production history
Designer Eugene Stoner (AR-16)
Arthur Miller
Designed 1963
Manufacturer ArmaLite (U.S.)
HOWA Machinery Co. (Japan)
Sterling Armaments Company. (UK)
Produced 1969–1985
No. built 1,171 (AR-18)
21,478 (AR-180)
Variants AR-18K
Foreign derivatives based upon the AR-18 include the British SA-80, Singaporean/British SAR-87 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 5.56×45mm 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 detachable box magazine
Sights Iron sights or removable 3× scope

The ArmaLite AR-18 is a gas-operated, selective-fire rifle chambered for 5.56×45mm NATO ammunition. The AR-18 was designed at ArmaLite in California by Arthur Miller, Eugene Stoner, George Sullivan, and Charles Dorchester in 1963 as an alternative to the ArmaLite 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 the United Kingdom, and it is said to have influenced many later weapons such as the British SA80,[1][2][3] the Singaporean SAR-80 and SR-88,[4] the American Adaptive Combat Rifle, the Belgian FN F2000[5], the Japanese Howa Type 89[6] and the German Heckler and Koch G36.[7] Through the Provisional IRA, which was noted for its use of the rifle, the rifle became known as the "Widowmaker".[8][9]


Soon after the adoption of the 7.62×51mm 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 offshoot 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. The ArmaLite 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,[10] a 'Carbine' Williams prototype carbine design in a .22 high velocity round which was similar to, but not interchangeable with, the .223 Remington (5.56×45mm). 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.[11][12] 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.[11] The AR-16 had a short, 15-inch barrel, hinged wooden butt, and weighed 8.75 pounds empty; only three examples were built.[12] Eugene Stoner left ArmaLite in 1961, shortly before Fairchild divested itself of ownership.[13]

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

Overall, the new AR-18 rifle is much more conventional than previous ArmaLite designs, although it uses 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.[14] 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.[15][16] 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.[14] 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 does not vent gas and carbon particles directly into the receiver.[17]

The AR-18's action is powered by a short-stroke gas piston above the barrel. The gas piston is 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 is vented from the barrel and travelled via a vent through the foresight housing into the hollow front section of the piston, which causes it to move rearwards a short distance. The rear end of the piston emerges through the barrel extension to contact the forward face of the bolt carrier, causing it in turn to move rearwards. The bolt itself is 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.[18] The bolt is moved into and out of the locked position via a cam pin that engaged a helical slot in the bolt carrier, which rides 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.[19] Unlike the AR-15, the cocking handle fits directly into a recess in the bolt carrier and reciprocates with it during firing, allowing the firer to force the breech closed or open if necessary. The cocking handle slot has a spring-loaded cover that can be closed by the user to prevent debris entering the receiver, and it will open automatically as the bolt carrier moves rearwards after the first shot. The recoil springs are housed within the receiver, differing from the AR-15 which houses its more elaborate buffer mechanism in the buttstock. The AR-18's compact design enables the use of a side-folding stock with a hinging mechanism (which proved to be less than adequately rigid).[16]

The sights are 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 is 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 is 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 hinge pin immediately forward of the magazine well.


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.[14] 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.[14] Between 1975 and 1978, no AR-18s or AR-180s were produced. From 1979 until 1985, the Sterling Armaments Company of Dagenham, Essex, in the United Kingdom produced the AR-18 and AR-180.[12][14] In mid-1968 ArmaLite set up pilot production in its Costa Mesa plant producing 1,171 AR-18s and 4,018 AR-180s between 1969 and 1972. Howa produced 3,927 AR-180s between 1970 and 1974.[20] Sterling manufactured 12,362 AR-180s between 1979 and 1985. In all, just 21,478 AR-180s were manufactured over 16 years between 1969 and 1985.

Operational use

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/M16, 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.[12] During the US trials at Aberdeen Proving Ground in 1964, the AR-18's functioning was found to vary from lot to lot of ammunition.[21] 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.[21] 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.[12] A number of deficiencies were listed and the testing authority stated that, although the AR-18 had military potential, it needed further development.[22] In 1968, dissatisfied with efforts to market the AR-18, Arthur Miller left ArmaLite.

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,[23] where the rifle was known as the "widowmaker" (see also Provisional IRA arms importation). The ArmaLite rifle was for many years the most lethal weapon available to the PIRA. For this reason, it become an iconic symbol within that movement. The Republican ballad "Little Armalite" tells of how the AR-18 changed the fortunes of the organization in their conflict with Britain.[24] The Armalite company reportedly bought 1000 copies of a recording for its salesmen to distribute.[25] The 1980s Republican political strategy of parallel political and paramilitary campaigns was also christened the "Armalite and ballot box strategy".[26] The AR-18 was also used by loyalist paramilitary groups such as the Ulster Volunteer Force, albeit in smaller numbers as they relied on examples captured from the IRA.


The standard AR-18 versions manufactured by ArmaLite, Howa and Sterling differ only in minor details. ArmaLite and Howa rifles have a satin gray phosphate finish, while Sterling rifles sported two finishes; Serial Numbers S15001 through S20000 had a black, glossy enamel painted finish. After S20000 a blued finish was used for the remainder of production.[27] Rifles were normally equipped with a sling, cleaning kit (bore/brush), and a knife-type bayonet with scabbard. An optional bipod with a case was available.

The AR-180 is capable of semi-automatic fire only and was externally identical in appearance to the AR-18 with one exception; the selector has only two positions, omitting the third "AUTO" position found on the AR-18. There are minor differences between the variants; to select "FIRE" on the Howa rifles the selector lever must be pivoted 180 degrees from "SAFE" so it is pointing forward towards the muzzle (where "AUTO" would be on a selective-fire rifle), while on the Sterling rifles, the "SEMI" position is the same as the "SEMI" position on a selective-fire rifle; 90 degrees from "SAFE" with the selector lever pointing down.[28] Towards the end of AR-180 production at ArmaLite's Costa Mesa shop in 1972, some unused AR-18 lowers were used to assemble AR-180s. The "SEMI" and "AUTO" positions were scrubbed and the "AUTO" position was relabeled "FIRE". The selector lever on these particular rifles would have to be pivoted 180 degrees from "SAFE" to "FIRE" the same way as Howa manufactured rifles.[29]

Sterling manufactured a small number of sporter variants called the AR-180 SCS, of which only 385 were reputed to have been made.[30] It has a large single-piece wooden thumbhole stock that replaces 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.[31] This version uses the same basic mechanism and folding butt, but has a 257 mm (10.1 in) barrel and a length of 765 mm (30.1 in) with the butt extended. The shortened barrel is fitted with a cone-shaped flash suppressor to address the additional muzzle flash resulting from the short barrel. Some examples have an additional pistol grip fitted to the underside of the handguard.

A 2.75× 20 mm telescopic sight was available but few were sold.[31] It is marked "ArmaLite", and has a quick-detachable, see-through mount that attaches 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 RSAF Enfield, the rival company of Sterling Armaments Ltd when developing the SA80.[32][33][34]

Recent developments

The ArmaLite brand was purchased in 1996 by Eagle Arms, a U.S. small 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.[35] 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. In 2007 the AR-180B was discontinued due to poor sales.


Nonstate users

See also


  1. ^ a b "A Historical Review of Armalite, page 5" (PDF). ArmaLite, Inc. January 4, 2010. Archived from the original (PDF) on July 7, 2011. Retrieved June 2, 2011."It’s especially interesting to note that the RSAF’s later 5.56mm rifle, the SA-80, (later adopted as the L85) was nothing more than a bullpup version of the AR-180"
  2. ^ "if you ever take an SA80 apart, or see a picture of one fully disassembled, then look very closely at the bolt and gas system, as it’s almost a direct copy of the old AR-18 system"
  3. ^"When[permanent dead link] the ArmaLite Model 18 was in its last days of production, weapons engineers at Enfield borrowed heavily from its design for ‘inspiration’ on their new 5.56mm rifle. Known then as the Enfield Weapons System and now as the L85, the bullpup rifle of the British military is at its heart a modified AR18 thrown into a radically different stock."
  4. ^ "Archived copy". Archived from the original on 2014-11-01. Retrieved 2014-11-01. "Borrowing a page from their Commonwealth partner, the Singapore-made SAR80/SR88 rifles have the same AR18 action. Nevertheless, the Brits got it honest, with both the Austrians and the Germans also using similar short-stroke gas piston layouts on the Steyr AUG and HKG36 rifles".
  5. ^
  6. ^ "89式5.56m小銃" (in Japanese). Archived from the original on 2008-12-24. Retrieved 2009-01-17.
  7. ^ "But the true legacy of the AR-18 is all the “modern” firearms that have adopted the bolt carrier group and operating system such as the H&K XM8 & G36, Bushmaster/Remington ACR, FN SCAR 16/17,South Korea Daewoo K1/k2,British L85A1/SA80 as well as the Singaporean SAR-80/SAR-88"
  8. ^ "A non-restricted AR in Canada AR180B". Silvercore Firearms Training. Archived from the original on 24 September 2015. Retrieved 25 May 2014.
  9. ^ Wharton, Kenneth (2011). Bloody Belfast: An Oral History of the British Army's War Against the IRA. The History Press. ISBN 9780752475981.
  10. ^
  11. ^ 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
  12. ^ a b c d e Walter, John, Rifles of the World, Iola, WI: Krause Publications, ISBN 978-0-89689-241-5 (2006), p. 42
  13. ^ Pikula, Sam (Major), The ArmaLite AR-10, Regnum Fund Press (1998), ISBN 9986-494-38-9, p. 92
  14. ^ 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
  15. ^ Dolazell, Harry, ArmaLite/Sterling AR-18 5.56mm Rifle, Colchester, Essex (UK): GunMart Magazine, Aceville Magazines Ltd. (2000)
  16. ^ 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.
  17. ^ "A Historical Review of Armalite, page 13" (PDF). ArmaLite, Inc. January 4, 2010. Archived from the original (PDF) on July 7, 2011. Retrieved June 2, 2011.
  18. ^ THE "Armalite AR-18/AR-180 Rifles: The Rifle that Never Could" By Christopher R. Bartocci
  19. ^
  20. ^
  21. ^ 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)
  22. ^
  23. ^ a b Bishop, Chris. Guns in Combat. Chartwell Books, Inc (1998). ISBN 0-7858-0844-2.
  24. ^ Patrick, Derrick (1981). Fetch Felix: the fight against the Ulster bombers, 1976-1977. Hamish Hamilton. p. 32. ISBN 978-0-241-10371-5.
  25. ^
  26. ^ McDonald, Henry; Cusack, Jim (2004). UDA: inside the heart of Loyalist terror. Penguin Ireland. p. 121. ISBN 978-1-84488-020-1. Retrieved 19 May 2013.
  27. ^
  28. ^ "An oddity regarding the AR-180 selectors; The Howa AR-180s are marked SAFE and FIRE and the selector rotates 180 degrees - the Sterling's and most Costa Mesa AR-180s are marked SAFE and SEMI and the selector rotates 90 degrees".
  29. ^
  30. ^ "ArmaLite Sterling AR180 SCS .223 Thumbhole Target Stock". Archived from the original on 2011-07-11. Retrieved June 2, 2011.
  31. ^ a b "ArmaLite AR-18: The Widowmaker". Archived from the original on March 17, 2011. Retrieved June 2, 2011.
  32. ^
  33. ^
  34. ^
  35. ^ "ArmaLite, Inc. AR-180B Rifle". Archived from the original on 7 June 2011. Retrieved June 2, 2011.
  36. ^
  37. ^ "89式5.56m小銃" (in Japanese). Archived from the original on 2008-12-24. Retrieved 2009-01-17.
  38. ^ "TAHUKAH ANDA SEJARAH VAT 69...???" (in Malay). [better source needed]
  39. ^

External links

  • "A Historical View of ArmaLite" Edition of 4 January 2010
  • Armalite AR18 and AR180 Operator's Manual
  • Armalite AR180B Operator's Manual dated June 2009
  • Modern Firearms article on AR-18
  • AR-180 Pictorial
  • Armalite AR-180: Move over AR-15/M16 — we take you back to the first piston-operated assault rifle
  • "Armalite / Sterling AR-18 5.56mm Rifle"
  • ArmaLite AR18 Rifles: Eugene Stoner’s ‘red-headed stepchild'
  • Gunlab blog article showing manufacturing stages of lower receiver
  • Gunlab blog article on AR180 upper receiver
  • Gunlab blog article on AR180 receiver stamping
  • Facebook group for AR-18,AR-180, and AR-180B.
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