BCM CQB 11 MCMR (SBR) (ALL NFA RULES APPLY). UPPER RECEIVER Receiver Machined from Aluminum Forgings 7075-T6 and Hardcoat Anodized per MIL-A-8625F, Type III, Class 2 M4 Feed Ramp Flat Top with Laser T-markings Carbine Gas System BCM® BOLT CARRIER GROUP Machined from MIL-SPEC Carpenter No. 158® Steel HPT/MPI (High Pressure Tested/Proof) · (Magnetic Particle Inspected) Shot Peened Tool Steel Extractor w/ BCM® Extractor Spring Black Extractor Insert Chrome Lined Carrier (Full Auto Profile) Chrome Lined Gas Key Hardened to USGI Specifications, w/ Staked Grade 8 Fasteners per MIL-SPEC BCM® LOWER RECEIVER Receiver Machined from Aluminum Forgings 7075-T6, Hardcoat Anodized (per MIL-A-8625F, Type III, Class 2) Low Shelf for RDIAS Installation - Installation of a registered drop-in auto sear allows weapon to fire on full automatic Low Shelf for Accuwedge use Fire Controls Marked SAFE and SEMI BCM® Milspec 7075-T6 Receiver Extension Staked M4 Lock Nut USGI H Buffer (1 USGI Tungsten, 2 Steel) BCM® BARREL Independently Certified MIL-SPEC 11595E Barrel Steel, Manganese Phosphate Barrel Finish on Entire Barrel 11.5" Standard Government Profile Barrel 1/7 Twist, M4 Feed Ramp Extension USGI 5.56mm NATO Chrome Lined Bore and Chamber HPT/MPI(High Pressure Test) (Magnetic Particle Inspected), per MIL-SPEC.