Saw an interesting thread on the AR-180 here, and not wishing to hijack it, I thought I'd post some of my research on this fascinating rifle. I acquired one many years ago, and like it immensely. Hope you find this of interest and helpful.
John
This out of the ordinary assault rifle was designed to be everything the AR-15/M16 series was not. Its structure was basically stamped steel. It had a gas system that did not vent gas into the bolt area. It had a folding stock for compactness, and it could be manufactured cheaply and easily in just about any backwater area in the world with relatively primitive equipment. In spite of many virtues, the selective fire AR-18 and semiauto AR-180 have now become relegated to collector status.
After adoption of the 7.62x51mm M14 rifle by the U.S. in 1957, the U.S. Continental Army Command looked into small-caliber high-velocity rifles, and prototypes were solicited. ArmaLite and Winchester responded. ArmaLite’s offering was the AR-15, which was a smaller version of their earlier AR-10, a 7.62x51mm rifle which had appeared too late to compete with the M14 prototypes. Military trials of these rifles dragged on for some time, and ArmaLite decided it could no longer afford to play. It sold the rights to the AR-15 to Colt, a decision I’m sure they regretted. Of course that rifle was subsequently adopted, the precursor to the M16 family of assault rifles still in service today.
Eugene Stoner, the chief designer for ArmaLite, afterward developed the AR-16, which was a folding stock assault rifle in 7.62x51mm. Instead of the direct-impingement gas system used by the AR-15, it used a short-stroke gas piston to give the bolt carrier a rearward push. The advantage was no gas fouling in the critical rotating bolt area, making the rifle much easier to clean and maintain. The bolt carrier and the bolt rode on two rods, each of which was surrounded by springs. The close tolerances of a traditional bolt raceway were eliminated. Most of the parts in the gun were steel stampings, enabling easy manufacture. A bolt handle directly attached to the bolt carrier allowed a forward push on the bolt if needed, and a folding stock was provided. This was Stoner’s last project for ArmaLite and he left shortly after designing it. Only a few prototype AR-16s were made, and this arm was never manufactured in quantity.
With the U.S. adoption of Colt’s AR-15, ArmaLite decided to try again to cash in on a logical evolution of the small-caliber high-velocity concept. Stoner’s AR-16 was essentially scaled down to fit the 5.56mm (.223) cartridge. The engineers involved were the new chief designer Arthur Miller, George Sullivan, and Chuck Dorchester. The new rifle was called the AR-18.
The AR-18 mimicked the AR-16 in almost all respects. There was a short-stroke 3-piece gas piston above the barrel. It moved back to contact the front face of the bolt carrier, pushing it rearward. A rotating 7-lug bolt similar to that on the M16 rifle was rotationally cammed by the bolt carrier to lock and unlock the bolt to and from the barrel collar at the rear of the barrel. The bolt carrier did not contact the receiver walls, but rode instead on two rods, each with its own return spring. This arrangement helped with reliability when dirt and debris were present in the receiver. Steel stampings were extensively used for easy manufacturing, and a folding stock was implemented, making the rifle ideal for tankers and paratroopers. This stock could be folded and latched against the lower receiver to the left, and the arm could be fired with the stock open or closed. An ambidextrous selector switch was used. The upper and lower receivers were joined by a cross pin in front and a locking catch in the rear. These receivers pivoted apart much like the M16. The magazines were similar to those used in the M16, but utilized a slightly different magazine release. M16 mags could be modified to work in a pinch by cutting a slot at a specific point in the side of the body of the mag with a Dremel tool. A stamped rear sight was utilized that was adjustable for elevation and windage, and a 2.75X quick-detachable scope made in Japan was available. This had an inverted post reticle and was range-adjustable, calibrated to the 5.56mm/.223 round. All in all, this was a good package that had a lot of appeal.
The AR-18 was put into initial production at its plant in Costa Mesa, California, and a semiautomatic-only version known as the AR-180 was also made there. These first rifles were basically machine shop fabrications and many of them show some hand fitting. A license to produce the AR-18 was sold to the Howa Machinery Company of Nagoya, Japan, and production was initiated there. However, Japan soon declared its neutrality in the Vietnam War, and production therefore ceased, as no military-style weapons could legally be exported to the combatants in that war. ArmaLite then turned to the Sterling Armaments Company of Dagenham, Essex in the United Kingdom to produce the rifles.
The AR-18 was evaluated officially by the U.S. in 1964 and the U.K. in 1966. In the U.S., the Army’s official decision was that the design was sound but needed development. Not happy with the company’s progress, Arthur Miller resigned from ArmaLite in 1968. ArmaLite made several minor changes, and the arm was re-evaluated in 1969. However, in spite of its merits, the AR-18 was not adopted, as the U.S. was already too heavily committed to the AR-15/M16.
ArmaLite then concentrated on civilian and police sales of these arms. Some small quantities were also sold to Botswana, Haiti and Swaziland. The outlawed Irish Republican Army liked the rifles immensely and nicknamed them the “widowmakers.” While the U.K. did not formally adopt the AR-18, many of its design features were used in the Sterling SAR-87 and the bullpup SA-80 family of British firearms. Other foreign weapons inspired by the AR-18 were the Japanese Howa Type 89, the Singaporean SAR-80, and the Australian Bushmaster M17S.
Minor complaints lodged against these rifles were that the folding stock became somewhat wobbly over time, and that there was no bolt release which could override the bolt hold-open feature when the magazine was empty. The fact that the magazines would not interchange with those of the M16 also worked against them on the civilian and police market. In all, the design still proved to be a compact, reliable, accurate and easily maintainable product that could be manufactured with commonly available equipment.
Other than prototypes made for evaluation, Costa Mesa produced 5,189 AR-18s and AR-180s from July 1969 to June 1972. Howa made 3,927 AR-180s from 1970 to 1974. These were particularly noted for quality. The rifle illustrated was made by Howa in early 1971, and is equipped with the ArmaLite quick-detachable scope. Sterling made 12,362 AR-180s from 1979 to 1985, of which 10,496 were imported into the U.S. Quality on the Sterling rifles varied. Some Sterling variants with wooden thumbhole stocks were made, as well as some short-barrel versions with cone-shaped flash hiders. 21,478 AR-18s and AR-180s were manufactured under the ArmaLite name by all plants from 1969 to 1985.
In recent years, a modern version of the rifle has been made as the AR-180B. It is marketed by Springfield Armory of Geneseo, Illinois. This rifle has a fixed stock integrated into a plastic lower receiver using AR-15 components, and utilizes AR-15/M16 magazines.
The AR-18 was a good concept, and had not the U.S. become so heavily invested in the M16, it could have been further developed to become the standard U.S. assault rifle. Many still swear by it today. This classic has become a hot collector’s item, with good examples bringing hefty sums when sold.