I am nothing like a metallurgist, but early in this game I saw that lead alloys (when listed by percentages of included elements) ALWAYS had smaller percentages of tin than of antimony. Lyman #2 was an exception, having the same percentage of tin and antimony (90/5/5). A friend gave me 65# of Ly #2 from Rotometals a few years ago, and that metal casts wonderfully and makes gorgeous bullets--but tin does cost the earth. Linotype is another nice metal to cast with, 4% tin and 12% antimony. Harder than woodpecker lips, too--and for most uses is a waste of the enriching elements.
So--seeing that Folks Who Know What They Are About use smaller percentages of tin than antimony in their bullet alloys, I mimicked their practices and got good outcomes. When in Rome, do as the Romans do. I have been playing around with 40/1, 30/1 and 25/1 lead/tin alloys for revolver and low-pressure rifle bullets (32/20, 38/55, 44/40, 45/70 at BP velocities) and had fun with them. Pretty accurate, and docile recoil. In rifles I used the Ross Seyfried formula--nominal BP weight x 0.4 = charge weight in IMR-4198.