An AR-15 style rifle is a lightweight semi-automatic rifle based on the ArmaLite AR-15 design, which is itself a scaled-down derivative of Eugene Stoner's AR-10 design. The then Fairchild Engine and Airplane Corporation division ArmaLite sold the U.S. Patent 2,951,424 and trademarks to Colt's Manufacturing Company in 1959, but after Colt's gas operated bolt and carrier system patents expired in 1977, Colt retained the trademark and is the exclusive owner of the "AR-15" designation. When manufactured with a barrel length less than 16 inches and without a shoulder stock, it is considered to be a pistol as opposed to being a rifle, and is described as an AR-15 style pistol.
