In 2015 I received a lot of help in getting started in casting bullets, from some very gracios members of the Cast Boolit Forum. I wanted a 700 grain, .585 bullet for cape buffalo that would perform as much like a North Fork Cup Point Solid as possible. Some of them laughed at me but several sages came through with instructions and a fairy esoteric recipe for the lead mixture. It was a success. I made up a life time supply. and never casted again.

At my low velocity the bullets were great. (Three, one shot kills.) The recovered bullets looked so good that I sometimes got requests for the recipe, but I had misplaced it.

Well here it is. I recently rescued it from my files.

- 10 lbs. of Lyman # 2 lead
- 7 lbs. of pure lead.
- 3 lbs. of old Hornady hard lead shot. (contained about 4% antimony)

This would make a good hard bullet if water dropped, but it would be too brittle and I was told it also needed some tin to "toughen it up." So they called for;

- 1 oz. of tin and 650 grains of copper sulphate. ( I think ?)

The copper sulphate was how you got the tin to mix with the lead, but my memory fails me on the protocol. One would have to raise the question on the Cast bullet Forum, but it went something like this: I think I melted the tin and copper sulphate together then poured them into a small batch if lead. ( As I write this part it doesn't sound quite right. Probably some one here will know what to do, for sure.) The point is that adding the Tin makes the bullet tough and the copper sulphate enables the tin the mix with the lead.
This is a very good DG bullet. It would be an excellent bear and moose medicine too, I think.

Seasons Greetings
Brian

the copper does not get the tin in solution.

the copper adds a boundary layer around the free antimony.

anyway you need zinc in the mix so you can trade the copper in and the zinc out.
removing the zinc will also remove about an equal amount of tin.
so put the tin in after making the ZN. Cu-S trade.