The AR-18 has its genesis in the AR-10. I n an effort to develop a less expensive version of that rifle, Armalite created the AR-12, an experimental rifle which used a stamped or bent sheet metal lower receiver in place of the forged AR10 lower. When Armalite sold the AR-15 patents to Colt, they had to stop using Stoner’s gas system, and so the AR-12 was refitted with a short stroke gas system copied form the SVT-40. This design would continue to evolve into the AR-16, a rifle still chambered for 7.62mm NATO, but using stamped construction for both the upper and lower receivers.
To meet the market for a cheaper 5.56mm rifle as a counterpart to the AR-16, Armalite engineer Arthur Miller scaled down the design in 1963/4, creating the AR-18. Armalite was hoping to find both military and commercial contracts for this new rifle, although no military sales would every develop. Armalite themselves built rifles in Costa Mesa (4018 AR-180 semiautomatic rifles and 1,171 AR-18 selective-fire rifles) between 1969 and 1972. In 1966 or 67 they arranged to license the design to the Howa company in Japan, who would make a further 3,927 of them. Shortly after the deal was made, however, the Japanese government restricted arms sales to nations at war, leaving Armalite looking for a new partner. In 1974 the license transferred to Sterling in the UK, who would make 12,362 AR-180s.
The rifle was tested sporadically by the US military between 1964 and 1970, but found to be not as good as the AR-15/M16. Sterling managed to make a few military sales in Africa, but nothing of major quantity. However the AR-18 mechanism would be the basis for many of the rifles in major military service for decades afterwards, including the British L85 and the German G36.
These were in the December 2019 RIA Premier auction. Hammer prices: AR18 (transferrable) – $23,000. How – $2,300. Sterling – $2,300. Costa Mesa – $2,588.