BCM builds professional grade weaponry manufactured, reinforced, and tested to meet the unforgiving needs of professional Soldiers, Law Enforcement, and responsible citizens in some of the most high threat environments in the world.Features:T-Marked Upper ReceiversM4 Feed RampsIndependently Certified Mil-Spec 11595E Barrel SteelChrome Lined Bore and ChamberManganese Phosphate Barrel Finish on entire barrelBolt machined from Mil-Spec Carpenter No. 158 steelHPT Bolt (High Pressure Tested/ Proof)MPI Bolt (Magnetic Particle Inspected)Shot Peened BoltChrome Lined Carrier (Auto)Chrome Lined Gas KeyGas Key Hardened to USGI SpecificationsGrade 8 Hardened Fasteners KeyStaked Per Mil-SpecTool Steel ExtractorBlack Extractor InsertReceivers Machined from Aluminum Forgings 7075-T6Receivers Hardcoat Anodized per MIL-A-8625F, Type III, Class 2Staked M4 Lock NutUSGI H Buffer (1 USGI Tungsten, 2 Steel)Low Shelf for RDIAS installationLow Shelf for Accuwedge useFire Controls marked Safe and Semi