The Heckler & Koch HK21 LMG is a germany-made select-fire lmg chambered in 7.62x51mm NATO, introduced in 1961. Primary use: military. Type: Machine Gun Action: Select-Fire Caliber: 7.62x51mm NATO Capacity: 100 Year introduced: 1961, Germany Weight: 256 oz Overall length: 47.5" Status: Active Intended use: military