WMD Guns Bolt Carrier Group BCG NiB-X nickel boron coated AR-15 M16 bolt carrier group designed for long life and easy cleaning. NiB-X coating provides enhanced wear resistance and a smoother surface to reduce fouling. Coating is guaranteed for life against chipping, spalling or flaking. Compatible with AR-15 and M16 platforms and benefits especially in short barrel setups and suppressed platforms. Includes all standard BCG components described below.