Thanks for your replies.
Chambering would require boring breach plug area forward; then making a sleeve with 50-95 chamber. As for pressure, I'd likely use the Lee modern minie at .500+/-; actually down sizing from the original Winchester diameter. Charge would be about the same, but with a lighter bullet than the 365 grain .514" I use in the lever gun. Not planning towards BPCRS, just trails and gongs.