When I run across scrap lead, the first thing I do is to melt it in a large pot outside, flux well and pour it into one pound ingots. I melt various lead alloys separately, and mark the ingots with a metal stamp so that I know what the alloy is as time goes by.
So I would start by doing that, and once they are in one pound ingots they can conveniently be mixed into a consistent casting alloy at the time you are casting.
So for your 45-70 you might use the wheel weights, add an additional 30% pure lead and a small amount of added tin from the mistake pile...not much, a total of 1% tin, and water drop.
Keep some pure lead for the black powder guns, and the solder and tin bearing alloys for boosting scrap lead you may run across in the future.
