HK’s MR556A1, shown here with the SureFire M900A vertical foregrip weapon light and an Aimpoint PRO with a 3XMag optic, features the same ultra-reliable gas piston system used by US Special Forces in the HK416, delivering premium performance in a patrol rifle.
Let’s face it, U.S. Special Operations units don’t scrimp on their equipment—nor do they stick with something if it doesn’t produce results. Given their use of and trust for Heckler & Koch (HK) firearms, it is not surprising that these units worked with that company in 2004 to develop the piston-driven AR carbine-style rifle that is known as the HK416.
The reputation this gun has earned among these elite warriors is due to its success in combat under the harshest conditions and its proven record of reliability, durability and accuracy. This, of course, almost immediately translated into a growing demand for a civilian version. Now, after many years of waiting, HK has introduced their MR556A1 rifle, which in many ways is an improvement over the military version.
I spoke with Wayne Weber, President of Heckler & Koch U.S.A. about the new rifle and he explained the difficulties that had to be overcome to offer a civilian version. This included dealing with subtle variations and improvements, to naming the new gun to the intricacies of US firearms import laws. Eventually all of these were resolved and the MR556A1 is now one of three HK firearms manufactured in the United States.
Based on the standard M4-style rifle, and still chambered in 5.56x45mm, the new MR556 dispenses with the old gas impingement system of operation for a new, proprietary short-stroke gas piston system. Anyone familiar with the standard AR gas system knows that all the gasses, fouling and carbon from firing a round are directed back through the gas tube into the bolt and receiver to operate the rifle.
lent accuracy, but only so long as the gun is kept clean and well lubricated—and therein lies the rub. With gasses going back into the bolt and receiver, it not only heats up quickly, especially in full-auto, but also makes the most important moving parts very dirty. Indeed, cleaning an AR rifle is a chore that no one craves.