My rifle boolits are typically air cooled wheel weight, with some added tin for good fillout. The old-time rifles you are shooting probably won't take real high pressure, so I wouldn't worry about casting your boolits real hard. If you check the swapping and selling posts, many members here are selling lead alloy of various compositions at reasonable prices. For pistol boolits I have been using range scrap plus tin (range scrap = bullets recovered from backstop and melted down.) If you are having trouble getting lead, send me a PM, and I might be able to help you out.
Where are you in PA? I'm next to Pittsburgh.
Wayne