Honestly ... I use a SAA clone, 4.75inch barrrel. Per their website, they proof test the pistols to 150% of the original loading. I don't really crank up to try and disprove them, but ...

Using a 250gr lead round nose, I can get velocities around 900 fps with smokeless or Pyrodex. Yea, that's "only" around 450 ft-lbs of energy, but have you looked a a 45 ACP? It's nearly identical (and if I recall, the ACP was made to get 45 Colt performance into a semi-auto platform). I also have some Buffalo Bore and Grizzly that's pretty hot but approved for SAA.

My grand idea was to pare it with an 1894. Turns out that rifle length only gets 1-200 FPS faster with those rounds. You can load up the round to push 13-1500 FPS from the rifle, but that's probably going to blow the SAA, and I refuse to be the guinea pig on that one.

Anyway, good luck, but don't be afraid of "only" the SAA.