Toolcraft .223/5.56/300 BLK M16 Profile Bolt Carrier Group - Nickel Boron - $99.95 The Toolcraft 5.56×45 NATO/.223 Rem (or .300 Blackout) Bolt Carrier Group comes in the Nickel Boron finish to reduce overall wear and friction, and for upgrading your existing AR build. These Full Auto M16 Profile