| 103rd | Top firearms |
| Armalite AR-18 | |
|---|---|
 AR-18 |
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| Type | Assault Rifle |
| Place of origin |  United States |
| Service history | |
| In service | None |
| Used by | See Users |
| Production history | |
| Designer | Gene Stoner (AR-16), Arthur Miller |
| Designed | 1963 |
| Manufacturer | Armalite (US), HOWA Machinery Co. (Japan), Sterling Armaments Company. (UK) |
| Produced | 1963–1980 |
| Variants | AR-18S, AR-180, AR-180B—foreign designs based upon the AR-18 include the British SAR-87, Singaporean SAR-80 and the Japanese Howa Type 89; bullpup adaptations include the British SA-80 and the Australian Bushmaster M17S |
| Specifications | |
| Weight | 6.6 lb (3 kg) (empty) |
| Length | 38 in (965 mm) |
| Barrel length | 18 in (457 mm) |
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| Cartridge | 5.56x45mm NATO |
| Action | Gas operated, rotating bolt |
| Rate of fire | 700–800 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, it has influenced many later weapons such as the British SA80, the Singaporean SAR-80 and SR-88, and the Heckler and Koch G36. It gained some notoriety through its use by the Irish Republican Army (IRA), who allegedly christened it the "Widowmaker".[1][2]
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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. Its competitor from Winchester was a remake of a 'Carbine' Williams prototype carbine design, which had been completed too late to prevent the adoption of the M1 carbine.
Main article: M16 rifle
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.
After Fairchild sold the AR-10 and AR-15 designs, ArmaLite could no longer use the patented direct gas impingement action of these rifles. Thus, Eugene Stoner began the development of a new rifle that used a more conventional short-stroke gas piston. The aluminum forgings of the AR-10 and AR-15 were replaced by steel stampings so that new design could be easily manufactured in foreign countries using available tooling and less specialized expertise.[3] Given that the SCHV concept had yet to be adopted, Stoner's new AR-16 was chambered in 7.62x51mm. When ArmaLite was reorganized, Stoner left the company. 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. With Stoner gone, responsibility for scaling down the AR-16 was given to ArmaLite's new chief designer, Arthur Miller. The resulting 5.56mm design was named the AR-18. Miller later received U.S. Patent 3,246,567 for the rifle in 1969.
Overall, the new designs were much more conventional than previous ArmaLite designs. They were immediately criticized for their appearance. At the time, crude sheet metal and welded components were frowned upon in the use of service rifles. However, such construction proved to be a sign of things to come, as it promised significantly reduced production costs, and allowed it to be made on less advanced machinery. Moreover, the gas piston operation of the AR-18 proved much more resistant to fouling than that of the earlier AR-10 and AR-15 rifles.
As mentioned earlier, the AR-18 was constructed from stamped steel upper and lower receivers and other components. Its action was powered by a short-stroke gas piston. 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. 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).
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.
ArmaLite's AR-16 design never progressed beyond prototype stage. However, the AR-18 was put into limited production, and underwent testing as an alternative to the AR-15. At this point, however, the AR-15/M16 rifle had been fully developed, flaws had been ironed out in successive modifications, and the U.S. military was not interested in acquiring yet another 5.56 mm service rifle.
Unlike the AR-15/M16, the AR-18 did not see substantial development over its life, and was not adopted in large numbers by any military service. In the end, the commercial failure of the AR-18 was not due to any significant flaws in its basic design, but in the lack of marketing efforts by ArmaLite. In 1968, dissatisfied with the way ArmaLite had marketed the AR-18, Arthur Miller left ArmaLite.
A semi-automatic version of the AR-18 design known as the AR-180 was later produced for the civilian market between 1969 and 1972 at Armalite's Costa Mesa manufacturing plant. The Costa Mesa AR-180s were one of the first military-type semi-automatic rifles to become widely available in the USA. Howa, of Japan, continued production of the AR-18/AR-180 from 1972 until 1974, but the Japanese government later forbade them to make war weapons, eventually axing the production. The Sterling Armaments Company of Dagenham, Essex, in the UK produced the AR-18/AR-180 from 1976 to the mid 1980s.
The ArmaLite brand was purchased in 1996 by Eagle Arms, a small US 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.[4] 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 is planned for production.
Although this rifle was not officially adopted by any nation as a standard service rifle, it was purchased for evaluation trials by various armed forces, including the United States and the United Kingdom. The rifles were also sold to civil users and on the international arms market. Some of these found their way into the hands of insurgents such as the Provisional IRA in Ireland amongst other places.
Despite its lack of commercial success, the AR-18's basic design features have been reused in several other firearms. These derivatives include:
   | Modern Firearms article on AR-18 - Modern Firearms - Armalite AR-18 assault rifle |
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