In revolvers generally if the loaded cartidge will chamber you will not need to size it. I have several lyman moulds that drop bullets that are a little large for the barrel but fit the chamber just fine. There are some people who have told me to slug the cylinders of the revolver and size to that. Holds down leading. Oversized bullets rarely lead. Undersized bullets however will. For a fact you need the Lyman cast bullet handbook. If your not in a hurry you can usually get one in pretty good condition at ebay or one of the other auction houses and save some bucks. MIght look there first. Good luck with your casting. Try not to get disgusted. It really is quite enjoyable after you get the hang of it.