The Heckler & Koch HK33 is a select-fire assault rifle designed and developed by Heckler & Koch. The HK33 was one of several designs that was heavily influenced by the Heckler & Koch G3 and was designed to accommodate NATO's 5.56mm round where as others chambered the 7.62×51mm NATO, the 7.62×39mm and the 9×19mm Parabellum.