The HK33 is a 5.56mm assault rifle developed in the 1960s by West German armament manufacturer Heckler & Koch GmbH (H&K), primarily for export. Capitalizing on the success of their G3 design, the company developed a family of small arms (all using the G3 operating principle and basic design concept) consisting of four types of firearms: the first type, chambered in 7.62x51mm NATO, the second—using the Soviet 7.62x39mm M43 round, third—the intermediate 5.56x45mm caliber and the fourth type—chambered for the 9x19mm Parabellum pistol cartridge.