A direct descendant of the world famous HK416, the MR556A1 is a semi-automatic rifle developed by Heckler & Koch as a premium-level commercial/civilian firearm. 

Like the HK416 and M27, the MR556A1 uses a proprietary HK gas piston and pusher-rod operating system in place of the gas tube normally found in AR15/M16/M4-style rifles. 

This closed system virtually eliminates malfunctions that are common in direct-impingement gas systems, since hot carbon fouling and waste gasses are not propelled into the upper receiver to operate the action. This feature is critical to the success of the HK416 used by elite military and law enforcement customers. 

The MR556A1 is assembled in the USA using US and German-made components and uses many of the same parts and assemblies developed for the HK416. It functions reliably and shoots accurately with a wide variety of quality 5.56mm or .223 ammunition. 

Like the HK416, the MR556A1 uses a barrel that is cold hammer forged in Germany from the highest quality cannon-grade steel. HK’s methodical process includes may steps omitted by other manufacturers to produce superior accuracy and service life. 

The principal difference between HK416 barrels and MR556A1 barrels is the lining. HK416 barrels are chrome-lined to ensure longer service life under fully-automatic fire. MR556A1 barrels are unlined for superior accuracy, while maintaining exemplary service life under semi-automatic fire. 

The MR556A1 barrel has six lands and grooves and a 1 in 7” twist. It is a taper-bore configuration with a slightly smaller internal diameter at the muzzle than at the chamber end for improved accuracy and velocity.

The MR556A1 is produced with the same commitment to quality as German-made HK firearms. By using joint US/German manufacturing Heckler & Koch leverages the relative strengths of two continents to make the preeminent AR-style firearm, combining the design innovations of the USA and Germany into one product. 




ID NumberUPC CodesDescriptionMSRP
MR556 Rifle, 5.56mm, Optics Ready - supplied with one magazine, rifle length M-LOK handguard, and medium contour barrel
81000579642230262553MR556, 5.56mm, Optics ready, 16.5" medium contour barrel, one 30rd magazine3,499
81000580642230262560MR556, 5.56mm, Optics ready, 16.5" medium contour barrel, one 10rd magazine3,499
MR556 Spare Magazines and Accessories
81000584642230262607MR556, Upper Receiver kit - includes bolt, buffer, buffer spring, rifle length M-LOK handguard and 16.5" medium contour barrel assembly2,069
251770S642230248311MR556 5.56mm 30rd magazine (steel)59
233609S642230245334MR556 5.56mm 20rd magazine (steel)69
235642S642230246492MR556 5.56mm 10rd magazine (steel)69
236204642230247642MR556 9" quad rail handguard379
50233617642230247635HK416 11' handguard416
51000223642230262157MR556 9" M-LOK handguard, black289
51001100642230262683MR556 12.5" M-LOK handguard, black299



CaliberStock Extended LengthStock Retracted LengthWidthHeightBarrel Length
5.56 x 45 mm37.68 in33.90 in3.07 in9.45 in16.5 in


CaliberRifle (without magazine)Magazine (empty 10 round magazine)
5.56 x 45 mm8.60 lb.31 lb

Other Specifications

CaliberMagazine capacityTrigger PullBarrel ProfileSight RadiusSights
5.56 x 45 mm10 or 20 rounds7.64 lb6 lands & grooves, right twist, 1 in 7 in14.60 invarious mechanical or optical sights


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