A direct descendant of the HK416, the MR556A1 is a semi-automatic rifle developed by Heckler & Koch as a premium level commercial/civilian firearm with match rifle capability. Like the HK416, the MR556A1 is a major product improvement over conventional AR-type carbines and rifles. The MR556A1 uses the HK proprietary gas piston operating system, employing a piston and a solid operating "pusher" rod in place of the gas tube normally found in AR15/M16/M4-style firearms. This method of operation virtually eliminates malfunctions that are common to direct impingement gas systems since hot carbon fouling and waste gases do not enter the receiver area. It uses many of the same assemblies and accessories including the HK free-floating four-quadrant rail system. The HK Free Floating Rail System (FFRS) handguard has four MIL-STD-1913 "Picatinny" rails and allows all current accessories, sights, lights, and aimers used on M4/M16-type arms to be fitted to the MR Series. It features a German-made barrel produced by Heckler & Koc's famous cold hammer forging process. The highest quality steel is used in this unique manufacturing process producing a barrel that provides superior accuracy and long service life. A precise enhanced two-stage trigger adds significantly to the accuracy of the MR556A1 and an extended latch charging handle makes operating the rifle with a telescopic sight easier. The retractable buttstock can be locked into a solid, non-moving position by tightening an Allen screw in the bottom of the stock. Special target rifle takedown pins ensure the upper and lower receivers are firmly mated for accurate performance.
- HK proprietary gas piston operating system
- HK Free Floating Rail System (FFRS) handguard has four MIL-STD-1913 Picatinny rails
- Picantinny rail machined into the top of its upper receiver
- German-made barrel produced by Heckler & Koch’s famous cold hammer forging process
- The unchromed barrel has an internal profile of 6 lands and grooves with a 1 in 7 inch (178 mm) twist. It is also moderately swagged with a slightly smaller internal diameter at the muzzle end than the chamber end
- A precise enhanced two-stage trigger adds significantly to the accuracy of the MR5556A1 and an extended latch charging handle makes operating the rifle with a telescopic sight easier
- Action: Semi-Auto
- Caliber: 5.56 NATO/.233 Remington
- Capacity: 30rd
- Barrel: 16.5" (1:7) with Flash Suppressor
- Sights: Diopter Front and Rear
- Upper Receiver: Aluminum Black
- Lower Receiver: Aluminum Black
- Stock: 6-Position Synthetic Black
- Grip: Synthetic Black
- Handguard: HK Free Floating Rail System Black
- Fixed Buttstock
- Trigger Pull: 7.64 lbs
- Length: 37.68"
- Weight: 8.6 lbs.