The M78 consists of two parts: the launcher and its power pack, which together weigh 15.2 kg. The gun itself is a 15 mW phased-plasma system that fires vaporized cadmium telluride pellets from a 30-round feed. The fast-discharge system powering the gun's laser and magnetic coil is fed from a 4 mW hydrogen fuel cell in the power pack. The firing cycle takes 3 seconds, most of which time is taken up by the powering up of the discharge generator.