I think you will like the No.1 Express round. The only problem is the brass is only available from Bertram's, if you want the headstamp. I believe it can be made from .475 No.2 NE, but it is quite a bit of work. The rims on 500's are too thin to use them as base cases.
I have a nice shooting load using 1 1/2F Olde Eynsford black powder, duplicating the original 110 grain black load with either 305 grain solids or 325 grain hollowed bullets - both paper wrapped.