Ar15 Full Auto Bolt Carrier, 56 NATO is the perfect solution for any shooter who needs rugged dependability in their rifle. 56 Black A NiB-X® nickel boron coated BCG sheds carbon buildup and offers exceptional lubricity for unmatched performance. Learn how the AR-15 bolt carrier group functions with this guide. LMT Piston Full Auto BCG Gen 2: Reliable and high-performing bolt carrier group for 5. Upgraded steel adjustable trigger mechanism MWS T8 SP Systems. 223/. Can be used legally in most semi-automatic rifles. 223/5. Shop WMD Guns M16 TiN M16/AR-15 Full Auto Bolt Carrier Group – POLISHED All WMD BCG components are manufactured by Defense Industrial Base suppliers to AR 15 Bolt Carrier Group Assemblies come in a variety of different styles from enhanced, lightweight, M16 profile, and more. 56 Full Auto BCG.