Ash - probably 2 7/8" chamber - and chambered for paper? - just a guess. the relationship between the front of the chamber's diameter to the bore's diameter will tell the case it was designed for. A small difference, say .030" to .060"- for brass, and .1.50 to .200" - for paper. These measurements seemed logical is all, not written down anywhere that I know of.

Brass cases, being so thin increase the capacity a great deal and would need much larger diameter and thicker (more of them) wads, of course.

BP and shot loads usually shoot amazingly well for the choke of the gun, but with cylinder bores, shooting even patterns can be frustrating. From a cylinder bore, heavy wads can tend to blow through the centre of the pattern, disrupting the shot into Donut patterns. A paper wrap around the shot can help a lot.