A direct descendent of the HK416, the MR556 is a semi-automatic rifle developed by Heckler & Koch

as a premium level commercial/civilian firearm. Like the HK416, the MR556 is a major product improvement of conventional AR-type carbines and rifles.

Using the HK-proprietary gas piston system found on the HK416 and G36, the MR556 does not introduce propellant gases and carbon fouling back into the rifle's interior, making it the most reliable of any AR-type firearm.

The MR556 will be produced at Heckler & Koch's new manufacturing facility at Newington, New Hampshire from American and German made components. To conform to German export regulations, certain design changes made in the MR556 prevents the rifle's upper receiver from being used on other AR-style firearms.

The MR556 uses many of the assemblies and accessories originally developed for the HK416 series arms including the HK free-floating four-quadrant rail system/handguard. This system allows all current accessories, sights, lights, and aimers used on M4/M16-type weapons to be fitted to the MR556. The HK rail system can be installed and removed without tools and returns to zero when reinstalled.

Like the famous HK416, the MR556 uses a barrel produced by Heckler & Koch's famous cold hammer forging process. The highest quality steel is used in this unique manufacturing process producing a barrel that provides superior accuracy for more than 20,000 rounds with minimal degradation of accuracy and muzzle velocity.

Production delays will prevent Heckler & Koch from meeting its delivery schedule on both the MR556 and MR762 rifles introduced at the 2009 SHOT Show in Orlando. Aside from finalizing the manufacturing process, HK engineers and technical staff in the U.S. and Germany are using the time to refine elements of the design, improve the quality of the rifles’ components, and ensure the final product is consistent with HK’s highest standards.