Helblaster Volley Cannon

The  Helblaster Volley Gun  is one of the most infamous black powder weapons ever invented, its devastating firepower able to tear apart an entire regiment in one thunderous volley. The lethal creation of the deranged Imperial Engineer von Meinkopt, its terrifying reputation has spread to all corners of the Old World. Its nine separate barrels are divided into three "decks" and are turned by means of a central crank, which means that it can unleash devastating hails of shot that engulf its unfortunate target in a firestorm of leaden death. Even heavily armoured Chaos Warriors can be shredded by a single volley, though with such devastating power comes great risk. Helblaster Volley Guns are notoriously prone to sudden, cataclysmic explosions. As a result, those crewmen who operate a machine so prone to catastrophically blowing them to tiny pieces tend to be paid up with the priests of Morr.

Source

 * Warhammer Armies: The Empire (8th Edition) -- p. 48