Volley gun
The Ribauldequin was a medieval version of the volley gun. It had its barrels set up in parallel. This early version was first employed during the Hundred Years' War by the army of Edward III of England, in 1339. Later on, the late Swiss army employed it.
Nock gun
The volley gun consisted of seven barrels welded together, with small vents drilled through from the central barrel to the other six barrels clustered around it. The central barrel screwed onto a hollow spigot which formed the chamber and was connected to the vent.