automatic screw machines, lathes, and presses. 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. The U.S. military's later adoption of the AR-15 gave legitimacy to its 5.56mm cartridge, and ArmaLite sought to develop a competing design chambered in 5.56mm that did not infringe on the Colt license agreement. With Stoner gone, it was decided to scale down the AR-16, and ArmaLite's new chief designer, Arthur Miller, embarked on the project. The resulting 5.56mm design appeared in 1963 and was named the AR-18. Miller later received for the rifle in 1969. Construction and design Overall, the new AR-18 rifle is much more conventional than previous ArmaLite designs, although it uses the relatively new stamped steel construction from its predecessor, the AR-16. Despite being pioneered by the Germans during WW2 in weapons such as the MP 44, and later adopted for the Soviet AKM, the use of stamped and welded sheet metal components was still uncommon in the manufacture of military rifles in the West in the early 1960s, which had, until then, largely retained the use of traditional machined forgings. Compared to the smooth lines of the AR-15, the AR-18 faced criticism over its stamped and welded construction, which had demonstrably greater tolerances in parts fit. However, the rifle proved to be both reliable and very accurate at all ranges up to . Its simple construction promised significantly reduced production costs, and allowed it to be license-produced locally on less advanced machinery, potentially reducing dependence on foreign manufacturers. The AR-18's action is powered by a short-stroke gas piston above the barrel. The gas piston is of three-piece design to facilitate disassembly, with a hollow forward section with four radial gas vent holes fitting around a stainless steel gas block projecting rearwards from the foresight housing. The gas is vented from the barrel and travelled via a vent through the foresight housing into the hollow front section of the piston, which causes it to move rearwards a short distance. The rear end of the piston emerges through the barrel extension