Add the hard-hitting punch of 450 Bushmaster to your lower receiver instantly. AR gas type operating system drastically reduces recoil for excellent second shot control. Aluminum forearm free-floats the barrel for optimum accuracy. Heavy barrel is hard chrome-lined in bore and chamber for exceptional durability and enhanced features. 1 in 24″ twist rifling, optimized for the .450 bullet. Includes 5-round .450 specific magazine.