The Armalite AR-18 is an assault rifle chambered for 5.56x45mm NATO ammunition. The AR-18 was designed by Arthur Miller, George Sullivan, and Charles Dorchester at ArmaLite in 1963 as an improved 5.56 mm caliber alternative to ArmaLite's previous AR-15 design, for which production rights had been sold to Colt Manufacturing Company. ArmaLite's interest in the design waned when the Colt AR-15 was selected for production by the US Army as the M16.