Given the popularity of our Gorilla Machining 16" 5.56 NATO barrels we’ve decided to release info. We start with top grade domestically sourced 4150 CrMoV Steel which is then drilled, reamed, button rifled, profiled and chambered in accordance with SAAMI Specifications. These barrels go through a battery of quality assurance checks each step of the way ensuring a remarkably consistent product every time. They are then finished with one of the nicest QPQ Nitride treatments you’ll find on an AR-Barrel. The end result is a barrel with deadly accuracy and rock solid reliability.