Hk Upper Mr556a4 5.56 11" Blk

The HK Upper MR556A4 5.56 11" Black is a premium piston-driven upper receiver assembly purpose-built for law enforcement, military, and civilian operators who demand reliability under sustained fire. Heckler & Koch's MR556A4 platform is the civilian iteration of the HG 416, one of the most battle-proven modern sporting rifles in active service with elite tactical units worldwide. This 11-inch barrel configuration delivers the ballistic performance and sight radius needed for CQB engagement and DMR-style precision work, making it ideal for those building compact yet capable rifle systems.

This upper receiver incorporates Heckler & Koch's proven short-stroke piston system—a design that reduces carrier tilt and prolongs component service life compared to direct impingement platforms. The 11-inch barrel is optimized for 5.56 NATO/.223 Remington ammunition and features a 1:7 twist rate suitable for a broad range of bullet weights from 55 to 77 grains. The flat-top Picatinny rail provides a solid mounting foundation for optics, and the integrated dust cover and forward assist ensure field reliability in demanding conditions. Finished in durable mil-spec anodized black, this upper is engineered to function reliably across extreme temperature ranges and high round counts typical of professional and defensive applications.

Operators building 11.5-inch to 12-inch short-barreled rifles, precision 300-yard platform configurations, or specialized CQB rigs will find this upper receiver compatible with any MR556A4-pattern lower receiver or AR-15-compatible lower with appropriate dimensioning. Law enforcement agencies deploying AR-platform carbines and military contractors value the MR556A4 upper for its piston reliability and reduced maintenance overhead in garrison and field operations. Installation requires standard AR-15 takedown pin and upper receiver group assembly procedures; no specialized tools are necessary. Verify lower receiver compatibility and local regulations before assembly and use.