The chambers only allow so much powder before the ball won't fit. Worse with conicals. Also, as has already been said, anything more than 40 would be a waste of powder. As with most weapons, going above a certain load just results in unburned powder being blown out the muzzle. IMHO you have nothing to gain by trying to push the outside of the envelope with a BP revolver.
It you arn't happy with that, then get a cartridge conversion cylinder for it. Then you can use 45 LC and be like your friends!
That's what I did.
Harry