Only problem with downloading slow powders is the velocity deviation increases usually quite a bit. Run them through a crono and make sure they are consistant. I'd suggest shorter cases or 44 special cases for downloading, start with the suggested amount of powder in a magnum case, measure the remaining space. Then subtract 1/8" powder, (and get a weight) cut 1/8" off case, (or go to a .44 special case) and run through the crono. My downloaded .454 loads deviate a lot more then the same bullets and same velocities from the .45 colt cases.