Armalite AR-18

   Developed in the late 1960s by the same company that devised the ubiquitous AR-15 and M16, the AR-18 was developed by Armalite to compete with Colt's M16. It was not a marketing success, but nonetheless left its mark on the development and history of military firearms.

   The AR-18 was an evolution of Eugene Stoner's AR-16, which was the last weapon designed by Stoner before leaving the Armalite firm, and it was a marked departure in design principles from his previous work on the AR-10 and AR-15. While the AR-16 retained the familiar gas operation and rotating bolt, it replaced the direct impingement system in the gas tube with a more conservative short-stroke gas piston. The AR-16 had also dispensed with the 5.56x45 mm caliber in favor of the larger 7.62x51 mm round, added an integral folding stock, and dispensed with the familiar AR-10 carrying handle.

   Though the AR-16 program was soon abandoned, other personnel at Armalite were assigned to develop an additional rifle based on its design. This effort was undertaken by a team led by George Sullivan, Arthur Miller, and Charles Dorchester, who were some of Stoner's partners in the design process of the AR-15 and AR-16. The end result of these efforts was the AR-18, which was essentially a simplified, scaled-down AR-16 re-chambered in the 5.56x45 mm round. Having lost rights to manufacture the AR-15 and the later M16 to Colt, Armalite intended to market the new AR-18 as a direct competitor.

   The AR-18 is similar in form and function to the ubiquitous AR-15, to the point where casual observers often confuse them. However, there are several marked differences in the design.

   Rather than the machined forging techniques employed in the M14, AR-15, and M16, the AR-18 was instead constructed using stamped and welded sheet steel, giving it much looser mechanical tolerances. The geometry of the receiver section has more in common with the AK-47 than the M16, with a reversed slant on the underside, and no carrying handle. However, the rear sight post is mounted on the back end of the receiver, not the front as on the AK-47. Unlike the M16, whose sling swivels are mounted on its front sight assembly and its stock, the sling swivels on the AR-18 are attached to the front slight assembly and the pistol grip; a design decision undoubtedly made due to the AR-18's integral folding stock. The magazine well accepts STANAG-type magazines.

   The stock is slimmer and lighter than that used on the M16, and is hinged at the base, allowing it to be folded. The foregrip is straighter and slightly broader than that used on the M16, and extends directly from the front of the receiver (there is no slip ring) to the back of the front sight assembly. The AR-18's pistol grip is angled like that on the M16 but more curved in shape. All three of the furniture components are made of plastic.

   Although the AR-18 is gas operated just like the M16, the former employs a short-stroke gas piston in its gas tube, rather than a direct impingement system. The AR-18's action also employs a rotating bolt, a feature widely-associated with the AK-47 family of rifles (and oddly less so with the AR-15 and M16, even though they use rotating bolts as well). Like on the M16, the AR-18 has a spring-loaded dust cover to prevent debris from entering the action, which opens automatically when the bolt carrier moves. Though unlike the M16, the cocking handle on the AR-18 moves with the bolt carrier via a slot on the side of the weapon during firing; this allows the user to force the breech open or closed by simply pushing or pulling it, which is a much more difficult task in the M16.

   The barrel of the AR-18 is manufactured using a ferritic nitrocarburizing process, eliminating the need for chrome plating in its construction. A three-pronged cylindrical muzzle brake is fitted, much like that on the early M16s.

   There is no bayonet lug on the AR-18; one presumably would have been fitted if it had been adopted by the US military.

   The rear sights of the AR-18 are flip-up type with two range settings (0 m and 200 m), while the front sights are a conventional post. A proprietary 3x telescopic sight may also be quickly fitted or removed, without any tools.

   Ultimately, the AR-18 was not accepted into service by the US military. Following a lengthy evaluation in the late 1960s, the official findings did concede that the AR-18 was in fact a superior and less expensive rifle than the M16, but it was rejected anyway on grounds that it was not enough of an improvement to overturn the procurement program for the M16, which the Pentagon had become heavily invested in (both financially and politically).

   Owing mainly to Armalite's failed offering to the US military, no nations have ever adopted the AR-18, but the AR-180 civilian model has ended up in the hands of non-state groups. Especially well-known for its use of the AR-180 in combat is the Provisional IRA.

   Sales efforts for the military models of the AR-18 were abandoned in the early 1970s, while the civilian models were produced from 1969 to 1985, and then briefly once more in the early 2000s. Though AR-18 variants have been manufactured by other companies, the original AR-18 series is no longer offered by Armalite.

   Though as outlined below, the AR-18 gave rise to a long and very successful series of assault rifles manufactured in other nations.

Variants

   AR-16: Prototype 7.62 mm assault rifle derived from the AR-15, and early design basis of the AR-18. Did not enter service.

   AR-18: Improved AR-16, most notably in the addition of a gas piston into its action. Did not enter mass production or service.

   AR-180: Semi automatic AR-18, made primarily for the civilian market. Production ran from 1969 to 1985.

   AR-180B: Modernized AR-180 with many new features and several different chamberings. Produced from 2001, but also discontinued due to poor sales a few years later.

   M17S: Bullpup AR-18 made in Australia by Bushmaster. Manufactured from 1992 to 2005.

   T65: Taiwanese copy of the AR-18. Used by Taiwan and the armed forces of 10 other nations.

   T86: Further development of the T65. Used by Taiwan and Jordan.

   T91: Further development of the T86. Used by Taiwan and the armed forces of 6 other nations.

   K2: South Korean copy of the AR-18, made by Daewoo. Used by ROKA and the armed forces of several other nations.

   AR-100: Civilian version of the K2, also a Daewoo product.

   Type 89: Japanese copy of the AR-18 made by Howa. Used only by the JSDF.

   SAR 80: Singaporean copy of the AR-18, made by ST Kinetics. Used by Singapore and 3 other nations.

   SAR-87: British copy of the AR-18, made by Sterling. Did not enter mass production or service.

   SR 88: Singaporean copy of the AR-18, made by ST Kinetics. Used by Singapore and Slovenia.

   L64/65: British prototype rifle, chambered in an experimental 4.85×49 mm round. Did not enter service.

Related Weapons

   AK-47/AKM: Soviet assault rifle with a similar operating principle. Used by many nations.

   Enfield L85/SA80: British assault rifle employing the AR-18 action, with an otherwise completely original weapon built around it.

   H&K G36: Has a very similar system of operation, though it is not actually an AR-18 derivative. Used by many nations.

   H&K HK416 and HK417: Modern M16-based rifles, made by Heckler & Koch in Germany. Though not derived from the AR-18, the addition of a gas piston made this weapon a spiritual successor.

   Magpul Masada: Rifle developed by Magpul Industries in the US, borrowing some design features from the AR-18. Replaced in development by the Bushmaster ACR.

   Bushmaster ACR: Improved Masada, manufactured in the US by Bushmaster. Used by Poland, and under evaluation by several nations.

   T2: Australian rifle similar to the AR-18, made by Leader Dynamics (later, by Australian Automatic Arms). The T2 was offered for sale to the ADF, but never found a military buyer. Civilian semi-automatic versions were manufactured from 1978 to 1996.

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