CMMG .45ACP Barrel and BCG Kit 5in 4140CM SBN Black. Unlike typical direct blowback systems our RDB uses a bolt that is forced to rotate and unlock slowing the BCG. This results in a lighter BCG for a lighter rifle and less felt recoil than a straight blowback system. MkG Barrel and Bolt Kits are designed to work exclusively with our MkG Lowers. Other manufacturers receivers may work but they cannot guarantee function or reliability. Specifications for CMMG .45ACP 5in Barrel and BCG Kit: Manufacturer: CMMG Color: Black Finish: Matte Fabric/Material: 4140CM Caliber: .45 ACP Barrel Length: 5 in Barrel Profile: Medium Taper Threads per Inch: .578x28 Barrel Twist Rate: 1-16 Flutes: No Gun Make: AR Platform Gun Model: AR-15 Weight: 1.6 lb Additional Features: Threaded Condition: New Dimensions: 1.90 X 1.95 X 14.75 in Package Contents: CMMG .45ACP 5in Barrel and BCG Kit What firearm models does the manufacturer say CMMG .45ACP 5in Barrel and BCG Kit is compatible with? The manufacturer suggests that CMMG .45ACP 5in Barrel and BCG Kit is compatible with AR-15CMMG 45D69FA: .45ACP Barrel and BCG Kit 5in 4140CM SBN Black