CMMG Bolt Carrier Group BCG AR15 6.5 Grendel/6mm ARC Black 64BA44F. 5 Grendel or Hornady'S New 6mm Arc. Will not work with our Mkw Platform. Is designed for Standard Ar variants. Specifications for CMMG Bolt Carrier Group (BCG) AR15 6.5 Grendel/6mm...