When picking components for your next mil-spec rifle build, having high-quality internal components that are guaranteed to mesh with your other mil-spec parts is a must, and the Faxon Firearms M16 Bolt-Carrier Group is designed to do just that. Machined from 9310 tool steel, the Faxon Firearms M16 Bolt-Carrier Group is heat-treated and shot-peened to military specifications and features a number of other features to enhance reliability, such as chamfering on the rear of the locking lugs. The BCG includes a spring, insert and Crane O-ring already installed. Designed for 5.56 NATO Chameleon PVD coating Magnetic particle inspected Thanks to the M16 profile of the Faxon Firearms M16 Bolt-Carrier Group, the unit is compatible with full-auto lowers and also features serrations compatible with the upper receiver's forward assist. Cartridge : 5.56 mm NATO Finish : Chameleon Make : AR-15