You are correct in the bullet size and black powder charge. There were also cartrides named .45-90 and .45-120 for the same reason. However you cannot use bullets for the 45-70 in a 45/50 sabot. The bullet you need to use are for a 45 cal revolver. Reason is that 45-70 bullets (45 rifle) measure .458" while 45 pistol/revolver bullets measure .451"-.452".