The only boolits I have cast so far are 9mm, and I have been using range scrap of unknown hardness. I now have a mold for a 300 Blackout AR I put together recently. I plan on loading subsonic rounds. I think I may need a harder alloy, maybe range scrap will be ok. I have a 5 lb ingot of superhard I could alloy in. Should I try it with just range scrap? If I need harder, how much superhard should I add as a starting point?