The harder the lead the harder it will be to load in a revolver. It will also come out of the mold a tad larger than pure lead because it wont shrink as much when it cools. .457 balls are generally used in Rugers. Pietta's and Uberti's do well with .454 balls. IMO trying to cram a hard lead .457 into a Pietta without using an off the gun loader is eventually going to end up breaking something in the loading lever assembly.