All I know is 20g of IMR 4227 under 255g SWC is a darn good load using a CCI-350 primer
. This isn't a 'hot' load either. It is my go to load at the moment in .45 Colt. I have not went higher with it, as I have no need for a hotter load. Around 1000fps is just right for me and I can shoot it in all my .45 Colt revolvers. I don't shoot jacketed so no experience there.
I did try it in .357 under 158g SWC, but I wasn't impressed... Tested from 10.2g to 14.0g. Again I don't shoot jacketed so no experience there.