HK MR556A4 Upper Receiver Kit 5.56 NATO 16.5″ Black

The HK MR556A4 Upper Receiver Kit is a high-quality upgrade for Mil-Spec 5.56mm AR-style rifles. This kit features the latest A4 enhancements, including a new barrel profile, adjustable gas block, and handguard. It includes a complete upper receiver/barrel assembly, enabling a retrofit to HK's piston and pusher rod system. This closed system minimizes malfunctions common in direct-impingement gas systems by preventing hot carbon fouling in the receiver area. Drawing from the HK416's proven design, this kit is assembled in the USA with US and German-made components and is compatible with a wide range of 5.56mm or .223 ammunition.

• Complete 5.56mm upper receiver/barrel assembly
• New A4 features including adjustable gas block
• HK piston and pusher rod system for reliability
• Compatible with Mil-Spec AR-style rifles

The HK MR556A4 Upper Receiver Kit is ideal for those seeking a reliable and accurate shooting experience. Please note, installation of Mil-Spec hammers on non-HK lower receivers is required for reliable function, and it is not compatible with fixed-stock AR/M16-type rifles. Explore this product at ICB Firearms, offering fast nationwide shipping and local pickup in Saint Clair Shores, Michigan.