FN America Barrel, 20, 556NATO, 1:7 Twist, Button Broached, Rifle Length Gas System, M16 Contour, Fits AR-15, Matte Finish, Black 20-100043 FN AR15 premium button rifled barrels are are manufactured using U.S. sourced Chrome Moly Venadium material per Mil-B-11595E. Each barrel is High Pressure Tested (HPT) and Magnetic Particle Inspected (MPI) to ensure that it is free of microstresses or flaws, resulting in consistency and quality in every barrel shipped from the factory.