Tks - that explains it, when he turned the guns sideways so the "idea" of a berdan-type ignition could be seen. If the priming was in a copper cup that helps seal the system it would be less of a burden to clean, otherwise, a nightmare. Maybe a nightmare anyway. It would have to use very small powder charge, or would become fouled very quickly or possibly blow the gun up from escaping gasses to the rear around the internal striker.
The metal action supports this premise.
The rifled balls are a "mechanical fit", instead of using a normal cloth patch. The bore would become badly fouled as well, if anything but a tiny charge was used.