Faxon Firearms Pencil Duty Series 5.56 NATO 10.5" Black Nitride 4150 CMVManufactured in house, these barrels are fully stress relieved, air gauge tested, and 11 degree target crowned to ensure superior accuracy. Quality is imbued into our barrels from the start. We start with the best materials, either certified 4150 Mil Spec steel or 416 R Stainless. From there, each barrel goes through a battery of tests at each operation until finished in Nitride and final inspected. All barrels are individually checked for headspace