The large socket and goes on a tiller, otherwise a staff or a long pike. I bet it was real heavy to wield in use. Each chamber is fired individually, many times by a second person so that the first person could hold and aim, while the second person would ignite it.
I have to believe that this was predominantly a defensive weapon, think like troops storming a fortification or palace and inside you can’t really wield a bow & arrow and you’re trying to rush down a hallway. A 2-person team at the end of the hallway could really stop an attack, never mind the“shock & awe affect” if they had never faced firearms in battle.
When arms like this were fielded in Europe, I think the most I’ve seen offhand has been 4 barrels, but most were individual barrels so that they could be wielded and aimed better. And after being shot, you still had a defensive pike/staff to use, with some type of steel pommel or point on the other end.
Recall that even in the age of musketeers, typically there would be a few pikemen around them to protect those ranks, especially from calvary charges.