The MR556A1 is the commercial carbine based off of the famous HK416 platform. With a lineage of proven reliability, durability and precision, the MR556A1 was baptized on the battlefield. Assembled in the U.S. using both German and U.S.-made components, using many similar components to the HK416 means this is the closest the initiated can get to owning the real thing. Like the HK416, the MR556A1 uses a proprietary HK short-stroke gas piston system instead of the direct gas impingement system found on lesser AR-15 style rifles. This closed piston system doesn't allow the exhaust gasses to enter the receiver, meaning the HK runs cooler, cleaner and more reliably. During adverse conditions with dust, sand and mud, the advantage of the HK system becomes even more evident, which is why many of the world's elite military units, law enforcement professionals and civilian enthusiasts have placed total trust in their HK's. Don't be overwhelmed as one would be when making such a decision, select the rifle that bears the name of Heckler & Koch.