Martini Man:
You don't say whether your preference is for black powder, or the 'nitro-for-black' equivalent loads. I shoot this cartridge in a Rodda double built by W&C Scott, which happens to be marked "CO EX" on the action flats indicating that it was built for the N-for-B load.

Here's a previous thread with my initial enquiry about loads, and some early results. This thread describes a successful hunt with that rifle.

I load 74gr AR2208 (Varget) beneath a 440gr JSP, with a couple of saddle-felt wads to take up the airspace. This matches original ballistics of 1675 fps and regulates perfectly in the vintage double. The beauty of a Martini single-shot is that you can load up quite a bit, because regulation is not an issue with only one tube, and the MH action is much stronger than most doubles.

If you toss in enough Varget to get the 440gr bullet up to about 1850 fps, you will probably still not exceed 11 or 12 tons pressure, quite safe in that action I would suggest. ...and a ripper hunting cartridge for moose, elk and bear with bonded-core bullets like the Woodleigh!

If you choose the acrid stench of brimstone in your nostrils, then someone else here will help you I'm sure! My definition of the "good 'ol days" does not extend back beyond the invention of smokeless powder!