This barrel is made of a proprietary blend of Hammer forged chrome molly vanadium made by FN that is referred to as "Machine Gun Steel" by virtue of its use in FN's M249 and M240 weapons.   The hammer forging process work hardens the steel over a tapered mandrel, making it more durable.  In addition, the chrome process for the bore allows for a lining almost twice as thick as a standard M16 for enhanced durability.  Chambered in 300 AAC Blackout, with a 1/8 twist, M4 barrel extension, and a pistol-length gas system.   This 10.5" barrel has an profile under the handguards optomized for better heat management and is Mil-spec phosphate coated, High Pressure tested and Magnetic Particle inspected.  Please check the barrel closely for any irregularities. It is the builder's responsibility to check headspace before assembling.  It is the buyers responsibility to kanow the NFA regulations on the use of this barrel.In the unlikely event you have an issue with a barrel, STOP AND DO NOT ASSEMBLE. Contact Customer Service. Barrel is non-returnable after it has been installed or modified.