Congrats on finding and recognizing a treasure. Many such have been trashed out of ignorance. My compliments on your enlightenment.
Bell ran the pressure tests alluded to above and reported in a series called "Finding Out For Myself" in DGJ. He pretty well "popped" the myth of differing time-pressure curves and low pressure for BP. Low pressure nitro in 2 3/4" cases is fine for most vintage applications.
For convenience, I'd suggest you load any of the 2 3/4" loads in any of the standard manuals for sub 7500 psi, 7/8 oz shot, and sub 1200 fps. Low pressure for the metal and low recoil for the wood and the shooter. I happen to have a good supply of PB, so it is what I use.
BP and short cases are fine for authenticity. If that trips your trigger, have at it. Consider brass cases while your are on this route, too. If, however, you find yourself with limited time to reload, consider the nitro route. Just be sure you know what you are feeding the 'ole hoss --- every time.
