The HK MR556A1 is the civilian semi-automatic version of the HK416 assault rifle. It uses HK's proprietary short-stroke gas piston operating rod system that keeps the bolt carrier group clean of carbon — the key innovation that differentiated the HK416 from the M4A1 it was designed to replace. The MR556A1 is German-manufactured to HK military production standards. Type: Rifle Action: Semi-Automatic Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 2010, Germany Weight: 92 oz Overall length: 36.9" Status: Active Intended use: military, law_enforcement, sporting, tactical