The
AR-18 is a
gas-operated,
selective-fire rifle chambered for
5.56×45mm NATO ammunition. The AR-18 was designed at
ArmaLite in
California by Arthur Miller,
Eugene Stoner, George Sullivan, and Charles Dorchester in 1963 as an 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, its production licence was sold to companies in
Japan and the
United Kingdom, and it is said to have influenced many later weapons such as the British
SA80, the Singaporean
SAR-80 and
SR-88, the American
Adaptive Combat Rifle, and the
Heckler and Koch G36. Through the
Provisional IRA, which was noted for its use of the rifle, the rifle became known as the "Widowmaker".