This .300 Blackout chambered 16 inch barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish and QPQ coated M4 feed ramp extension.
Quench Polish Quench (QPQ) is a specialized type of nitrocarburizing case hardening that increases corrosion resistance. It is sometimes known by the brand name of Tufftride, Tenifer Black Nitride or Melonite. QPQ is a huge improvement over Chrome Lined barrels. Unlike chrome lining, where the chrome is built up on the surface, QPQ converts the surface without the risk of dimensional build up. The technique is used when two or more of the following properties are required in a work piece: