A friend gave me a big bag full of 400gr 45-70 boolits as cast. I want to try PCing them but realize I will have to size them before loading. One thought I have is to use an old reloading die that I can add an insert to with a proper .458" through hole - I do have a lathe and am capable enough to machine such a part or lacking a die with a suitable through hole, I could machine the whole thing, threads and all. Is cold rolled sufficient for this purpose or do I need to buy a hunk of 4140 or other half hard kind of steel? Thanks for helpful responses!