 The AR-12 originally featured a direct-impingement (DI) gas operation system, but this was changed to a more conventional short-stroke gas piston in the AR-16 after ArmaLite sold the production rights to the DI system to Colt Firearms.The AR-16 had a short, 15-inch barrel, hinged wooden butt, and weighed 8.75 pounds empty; only three examples were built.Eugene Stoner left ArmaLite in 1961, shortly before Fairchild divested itself of ownership.