Best see how and if the action was proofed before deciding on converting it.
I converted a 16 gauge side by side to 45 colt, and working on a 30-30; but the big issue on handling any sort of pressure, aside from if the action can take it, is that you may need to bush the strikers for smaller primers.
Don't ask me how I know.
Making it black powder certainly helps the cause, but you want to be safe.
