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| | The AR-18 was created as a result of the US military's testing and adoption of the AR-15 rifle as the M16. During the protracted 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 into an independent company, and allowed the new owners to buy the rights for all of the company's designs except for the AR-10 and AR-15. When the U.S. military ultimately selected the AR-15 and adopted it as the M16, ArmaLite could no longer profit from its adoption. This created the need at the company for a new design that could generate revenue for the company. The U.S. military's adoption of the AR-15 had given legitimacy to the 5.56mm intermediate cartridge, so ArmaLite sought to develop a competing design chambered in 5.56mm that did not infringe on the Colt license agreement. They looked through the catalogue of designs they owned the rights to, and found promise in the AR-16 design. | | The AR-18 was created as a result of the US military's testing and adoption of the AR-15 rifle as the M16. During the protracted 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 into an independent company, and allowed the new owners to buy the rights for all of the company's designs except for the AR-10 and AR-15. When the U.S. military ultimately selected the AR-15 and adopted it as the M16, ArmaLite could no longer profit from its adoption. This created the need at the company for a new design that could generate revenue for the company. The U.S. military's adoption of the AR-15 had given legitimacy to the 5.56mm intermediate cartridge, so ArmaLite sought to develop a competing design chambered in 5.56mm that did not infringe on the Colt license agreement. They looked through the catalogue of designs they owned the rights to, and found promise in the AR-16 design. |
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| − | The AR-16, a 7.62mm NATO select-fire rifle, was Eugene Stoner's final design for ArmaLite prior to his leaving in 1961, shortly before Fairchild divested itself of ownership. 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 still modern select-fire military rifle that, unlike the more complex AR-10 and AR-15, could be cheaply produced from heavy-gauge sheet metal using automatic screw machines, lathes, and presses. The AR-12 originally featured a direct-impingement (DI) gas operation system like that found on the AR-15, but this was changed to a short-stroke gas piston system in the AR-16 after ArmaLite sold the rights to the DI system to Colt. ArmaLite opted to use the AR-16 design as a base for their new rifle, and ArmaLite's new chief designer, Arthur Miller, embarked on the project. The resulting design, chambered for the 5.56x45mm cartridge, would be finalized in 1963. | + | The AR-16, a 7.62mm NATO select-fire rifle, was Eugene Stoner's final design for ArmaLite prior to his leaving in 1961, shortly before Fairchild divested itself of ownership. 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 still modern select-fire military rifle that, unlike the more complex AR-10 and AR-15, could be cheaply produced from heavy-gauge sheet metal using automatic screw machines, lathes, and presses. The AR-12 originally featured a direct-impingement (DI) gas operation system like that found on the AR-15, but this was changed to a short-stroke gas piston system in the AR-16 after ArmaLite sold the rights to the DI system to Colt. ArmaLite opted to use the AR-16 design as a base for their new rifle, and ArmaLite's new chief designer, Arthur Miller, embarked on the project. The resulting design appeared in 1963, and was named the AR-18. |
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| − | One of the more striking aspects of the AR-18 is its stamped sheet metal construction, which despite being pioneered by the Germans during WW2 in weapons such as the MP 44 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. 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 the fitment of parts. 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 license-produced locally on less advanced machinery, potentially reducing dependence on foreign manufacturers. The AR-18's action is powered by a short-stroke gas piston above the barrel, while the bolt is in a similar configuration to the one found on the AR-15, with seven radial locking lugs engaging corresponding recesses in the barrel extension and the extractor in place of the eighth lug. 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. 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, as opposed to 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). The magazines were of a brand new proprietary design, and lacked the magazine-catch cutouts of the AR-15 magazines. Sterling later produced black-enameled steel magazines in 20- 30- and 40-round capacities that did have cutouts and were able to feed from an AR-15. However, the AR-18/AR-180 was never capable of using the Colt AR-15/M16's stock 20- or 30-round STANAG magazines.<ref name = "ar18 forgotten weapons">[https://www.youtube.com/watch?v=sRYPM-sKW74 Forgotten Weapons video on the AR-18]</ref>
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| − | The AR-18 was put into limited production at ArmaLite's machine shop and offices in Costa Mesa, California. ArmaLite was never equipped to build small arms at the scale needed to equip an army, and so sought to license the design out to a larger manufacturer. A license to produce the AR-18, and the semi-auto AR-180, would be sold to the Howa Machinery Co. of Japan, and the rifle was produced there from 1970 until 1974, when new controls on the export of military arms by the Japanese government forced the company to cease production. Between 1975 and 1978, there was a brief pause in production as ArmaLite finalized an agreement with the Sterling Armaments Company of Dagenham, Essex, in the United Kingdom, and from 1979 until 1985 Sterling would produce the rifles under license.
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| − | Unlike the AR-15/M16, the AR-18 did not see substantial sales success and was never officially adopted by any country as its 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 in 1964 and the United Kingdom in 1966. During the US trials at Aberdeen Proving Ground in 1964, the AR-18's functioning was found to vary greatly depending on the ammunition it was fed, and 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. The British Ministry of Defence (MOD) tested the AR-18 in March 1966, and found the design's performance during mud and sand trials to be unsatisfactory. 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. Again, a number of deficiencies were listed and the testing authority stated that, although the AR-18 had military potential, it needed further development. n 1968, dissatisfied with efforts to market the AR-18, Arthur Miller left ArmaLite.
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| − | While the AR-18 was never adopted as the standard service rifle of any nation, the AR-18 gas system is the ancestor for the majority of short-stroke piston gas systems found in modern military rifles. Rifles which use a copy or derivative of the AR-18 gas system include: the German HK G36 and HK 416, the Belgian FN F2000 and FN-SCAR, the Austrian Steyr AUG, the Czech CZ 805 BREN, the Chinese QBZ-95, the South Korean Daewoo K1, the Japanese HOWA Type 89, the Singaporean SAR-88, the Taiwanese T-91, and the British SA80 family of weapon systems.
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