Black Rain Ordnance Bolt And Carrier Group Nickel Boron .308 Caliber. Black Rain Ordnance (BRO) biohazard engraved on the spine of the carrier. .308 Caliber. Specifications for Black Rain Ordnance Bolt And Carrier Group (BCG) Nickel Boron .308 Caliber BRO-BCG-308: Manufacturer: Black Rain Ordnance Color: Silver Finish: NIB Carrier Material: 8620 Steel Bolt Material: Steel Caliber: .308 Winchester Hand: Right Condition: New Projectile Caliber: .308 Caliber The Black Rain Ordnance Bolt And Carrier Group Nickel Boron .308 Caliber BRO-BCG-308 is a quality addition to the Black Rain Ordnance lineup. For more great deals on Bolt Carrier Groups by Black Rain Ordnance please browse our Black Rain Ordnance Gun Parts page. Black Rain Ordnance Bolt And Carrier Group Nickel Boron .308 Caliber