I checked (http://www.lasc.us/CastBulletNotes.htm) to see what the minimum amount of Tin is needed to help fill out the mold. I didn't find exactly what I wanted, but I did find this:
It looks like anything over 3% may not be good.Add 2% - 3% tin when casting bore slugs from stick-on wheel weights to aid in mould fill out.
Linotype and Lyman # 2 alloy's have the lowest hardening potential of common bullet alloys because of the higher tin content (4% & 5%) and lack of arsenic.
I also want to be able to heat-treat the boolits, or make them harder by water-dropping from the mold.
Can anyone confirm the minimum amount of tin needed for pure lead with some antimony and NO arsenic? If the % of antimony makes a difference, then consider 6-8%.