The Heckler and Koch HK13 is a German delayed blowback selective fire light machine-gun designed to complement the HK33 rifle. It was one of the first 5.56 mm calibre machine-guns produced, entering production in 1972. It takes a 20-, 30- or 40 round box magazine, interchangeable with the HK33 rifle, and has a cyclic rate of fire of 750 rounds-per-...