You getting very good advice.

You can send the gun to Birmingham or Liege and have them proof it for a fee. The black powder loads you are considering were considered full power hunting loads in their day.
Pictures of the old proof benches always showed a solid wall in between the guns and the testers.
Measurements are taken with instruments that have been calibrated and certified to assure accuracy. These measurements are taken before and after the proof.
Here is a thread on the subject of proofing that you may find helpful.

http://forums.nitroexpress.com/showflat....=&fpart=all

If you are concerned about shooting any load in this gun, send it to a knowledgable sxs gunsmith to be inspected. Until the gun is completely disassembled, you will not be sure. In addition, the barrel walls have to be measured.

I had an older gun inspected. Upon disassembly it showed a crack in the interior of the frame. I had the crack welded. This gun had fluid steel barrels. I would hate to think how many shells of any pressure it would have handled before the frame simply failed.


Pete