In use would they load with a standard charge or a lighter charge? I wish I had taken a picture of the bore. Reboring to fire a twelve pound ball would have to have made the tube dangerously thin. If it actually saw much use, I'm surprised it survived.
Light gun, so more maneuverable than heavier guns and since one can't expect much range from it, I could see where the majority of the basic ammunition load would be cannister/grape shot - like a big two-wheeled sawed-off shotgun.