The Colt LE6921SOCOM M4A1 Upper Receiver Conversion Kit is a complete centerfire upper receiver group chambered in 5.56mm NATO, meticulously engineered to match the early Global War on Terror (GWOT) deployment configuration of the U. S. military’s M4A1 SOCOM battle rifle. This highly collectible factory kit provides a drop-in option to convert any standard AR-15 lower receiver into a milestone-correct, mil-spec tactical weapon system. It features a true 14.5-inch chrome-lined, button-rifled SOCOM heavy barrel with a 1:7" right-hand twist rate, a standard carbine-length direct gas impingement system, a fixed A2 front sight tower with an integrated bayonet lug, and a side sling swivel. The historical, premium presentation is heavily upgraded right out of the box with military-contract components, including a genuine Knights Armament Company (KAC) RAS quad-rail handguard accompanied by polymer rail covers, a KAC vertical foregrip, and a premium mil-spec MaTech folding backup rear iron sight (BUIS). Colt LE6921SOCOM 5.56mm 14.5" Heavy Bbl KAC Rail Matech BUIS Matte Black Upper Receiver Conversion Kit LE6921SOCOMCK