Nearly two decades of building the finest custom tactical AR-15 rifles have given us the insight to develop a comprehensive line of stainless steel, match grade barrels that offer superior accuracy, reliability and longevity for your next custom AR rifle project.All Wilson Combat Match Grade AR-15 barrels are precisely crafted of the finest American-made 416R rifle rated steel on computer controlled equipment to our exacting list of technical specifications. These proven barrels feature a hand-polished bore and feedramps and then complete a rigorous final inspection process that ensures your new barrel will meet your most demanding expectations. All barrels feature crisp CNC markings, precision muzzle crown and a chamber and gas port optimized for reliability.5.56 NATO5.56 NATO was developed in the United States and initially chambered in the M16 rifle. It is the standard cartridge for NATO forces as well as many non-NATO countries. It is derived from, but not identical to, the .223 Remington cartridge. We use a NATO, mil-spec chamber in our barrels that is reliable and safe to fire both 5.56 and .223 Remington rounds. This common and easy-to shoot cartridge is ideal for defense, training and small-medium game hunting.Specifications: Chamber: 5.56 NATO Feed Ramps: M4 Style Finish: Matte Bead-Blasted Stainless Gas Block Seat: .750 Diameter by .920 Length - Dimpled for Set Screw Gas System: Intermediate-Length (Wilson Combat Only 13.25) Length: 16 Material: Stainless Steel, Type 416R, Barrel Grade Muzzle Threads: 1/2 x 28 Profile: Paul Howe Tactical Carbine Rifling: 1:8, Precision Button Rifling Weight: 28.6 oz.