I'm feeling lazy, right now, so I'm not gonna go to "The Book". Howsomever, I used to load 5.8 gr. of 231 behind a 200-gr. .45ACP, 5" barrel to get 850 ft/sec. So, I'd guess around 7 gr. of 231 in the shorter barrel and the heavier bullet would put you in the ball park.
I used the 5.8 grain powder charge (too lazy to change the powder measure) behind 250-gr lead bullets in my Red Hawk, but that has the 7-1/2" barrel. It definitely knocked down steel plates harder than the .45 Gummint...
Go buy a book!