I was looking at Greame wrights book for BP double rifles
.360- 2.25 BP 50grain, 155 g bullet. 10 tons pressure 1700 ft sec 993 ft lbs
.450 3.5”. BP120 g , 270g bullet 11 tons 1975 ft sec 2336 ft lbs
.500 3”. BP 136g, 340g bullet , 11tons, 1925ft sec. 2794 ft sec