Ready To Install To Make A Reliable, Clean Running Piston Carbine Or Pistol Complete Tactical Elite upper receiver assembly comes ready to install on mil-spec lower receiver to produce a reliable, positive-cycling gas piston gun. Adams Arms’ proven piston system doesn’t vent hot gases and burned powder into the bolt carrier and receiver, so the gun runs cooler, with less fouling and wear on the action, and easier maintenance. Short-stroke piston shaft eliminates concussive gas expansion in the upper receiver for less violent cycling, smoother feeding, and reduced felt recoil. The receiver is forged from 6061 T6 aluminum and features M4 feed ramp cuts and a 13-slot Picatinny-cut flattop rail. The adjustable gas block allows three levels of gas release: normal fire, firing with a suppressor attached, or a single round fired without cycling. Picatinny rail on top of gas block accepts a variety of clamp-on tactical sights. All models have chrome-lined barrels chambered for 5.56mm NATO, with an A2 flash hider and a black Melonite® finish for superb wear resistance and up to 60% more corrosion resistance than traditional phosphate coating. Pistol - 7½" barrel and two-piece, machined aluminum handguard with four, 3" Picatinny rails. Pistol Extended Rail - 7½" barrel and an extended, aluminum handguard with 6" side rails, a 5¾" bottom rail, and a 4¼" top rail that forms a continuous 12" rail with the receiver flattop and gas block. Mid-Length - 16" barrel with extended 12" handguard. Side rails include sockets for QD sling swivels. All NFA rules apply.