Our groundbreaking MCR® (Mission Configurable Rifle) belt-fed upper receiver assembly is designed to interchange with standard AR/M4 type uppers and readily fits any MIL-Spec lower receiver without permanent modification to the host lower and is rearward compatible to AR15/M16 models produced as early as 1963. The MIL-Spec MCR® 5.56 DFR takes our standard MCR® technology to a whole new level and includes all of the accessory items that are included in our standard MCR® government product along with Dry Film Lubrication on critical high-friction surfaces for extra performance in extreme conditions. - Once installed the patented MCR® upper receiver system can be user-configured in seconds without tools to adapt to virtually any mission profile. Specifically designed for responsible armed citizens law enforcement and professional security personnel who wish to upgrade their rifle or carbine to MCR® performance and capability; standard features include gas-piston operation for extreme reliability in adverse conditions; a 12.5 quick-change (3 seconds) barrel system and a MIL-STD 1913 co-planar hand-guard with rail-interface system for the mounting of optics and modern accessories. Spanning the capability range from the optic ready carbine through a lightweight support rifle; the MCR® accepts standard box type AR15/M16 magazines or M27 linked ammunition at operator discretion permitting unprecedented firepower and weapon flexibility. - KEY FEATURES - Drop-On (MIL-Spec) Upper Receiver Assembly that upgrades your AR15/M16/M4 type lower receivers or rifles - 5.56 x 45mm NATO - 12.5 Quick-Change Barrel - 1:7 RHT ½-28 TPI - Short-Stroke Gas Piston Operation - Dual-Feed- Accepts ALL AR15/M16 Magazines & M27 Linked Ammunition - Precision Machined 7075-T6 Billet Upper Receiver Feed Cover and Charging Handle - Precision Machined Billet Steel Feed Tray - Finish- Manganese Phosphate & Type III Class 2 Hardcoat anodize - Black for Maximum Corrosion and Wear Resistance - Dry Film Lubricant Applied to Critical High-Friction Surfaces - Full-Auto Bolt Carrier - Handguard Style MIL-STD 1913 Rail - Adjustable Sight Set - Quick-Change Barrel Handle - Ships with Belt-Feed Main Action Spring MIL-Spec H3 Buffer Carbine Stock Spacer Extended Bolt Catch Mag Adapter RIP Brake Muzzle Compensator (100) M27 Links & Operator's Manual - Made In USA