The MR556A1 is HK's civilian version of the HK416, sharing the piston-driven system, bolt, and barrel with the military variant while meeting US import requirements with a thumbhole stock. Type: Rifle Action: Semi-Automatic Caliber: 5.56 NATO Capacity: 30 Year introduced: 2010, Germany Weight: 112 oz Overall length: 37" Status: Active Military use: Yes Intended use: Sport, Tactical, Military Analog