M4 Feed Ramp Barrel Extension. M4 Feed Ramp Flat Top Receiver. Government Profile Barrels. Independently Certified Mil-Spec 11595E Barrel Steel. Chrome Lined Bore and Chamber. Manganese Phosphate Barrel Finish on entire barrel. Bolt machined from Mil-Spec Carpenter No. 158® steel. HPT Bolt (High Pressure Tested/ Proof). MPI Bolt (Magnetic Particle Inspected). Shot Peened Bolt. Chrome Lined Carrier (AUTO). Chrome Lined Gas Key. Gas Key Hardened to USGI Specifications. Grade 8 Hardened Fasteners Key. Staked Per Mil-Spec. Tool Steel Extractor. Black Extractor Insert. Receivers Machined from Aluminium Forgings 7075-T6. Receivers Hardcoat Anodized per MIL-A-8625F, Type III, Class 2. Staked M4 Lock Nut. USGI H Buffer (1 USGI Tungsten, 2 Steel). Low Shelf for RDIAS installation. Low Shelf for Accuwedge use. Fire Controls marked SAFE and SEMI.