Rotometals sells a lead-free bullet alloy consisting of 87.25% Bismuth, 0.75% Antimony and 12% Tin. It is a bit more picky about fit to the throat of the chamber. A homemade version (bismuth shot salvaged from some shotshells loaded with bismuth shot alloyed to roughly the same proportion of tin using 95-5 (tin to silver) solder seemed to do about as well. Either version isn't cheap--around $17-20 USD/pound--but they seem to function OK as a hunting alloy.

I've played with them a bit in ML guns and one of my Krags. It wants to be cast at about 500 degrees F. No problems with soldering in the mould, or fouling problems in the Krag.

YMMV of course, but it might be worth a look.