The United States military has trusted FN America to produce the guns used by our troops in combat zones across the world, and now, you can pick up the same U.S.-made M16 barrels used by our troops for your own AR-15. Each FN AR-15 BB M16 barrel is machined from chrome-moly vanadium steel sourced right here in the United States. After button-rifling, each FN AR-15 BB M16 barrel gets a chrome-lined bore and chamber that prevents corrosion and also minimizes heat erosion. This helps to extend the life of your rifle, as well as enhance reliability. After chrome-lining, each barrel is high-pressure tested and MPI-inspected to ensure it meets all military standards. Outside, the barrels are treated with a manganese-phosphate finish that resists corrosion. These FN AR-15 BB M16 barrels are all chambered in 5.56 NATO and are available in the following barrel and gas-system lengths: 10.5-inch Government Carbine, 14.7-inch Government Mid-length, 16-inch Government Carbine, 16-inch Government Mid-length, 18-inch Government Rifle, 20-inch Government Rifle.