 While some sources call the MAC-10 and MAC-11 machine pistols, the guns are also referred to as compact submachine guns.Since it is difficult to control machine pistols when they are fired in full automatic mode, in the 1970s, some manufacturers developed an "intermittent-fire" setting that fires a burst of three shots instead of a full-automatic, such as the Heckler & Koch VP70.It is a 9 mm Parabellum, 18-round, double action only, select fire capable polymer frame pistol.