Just a thought - If Solder can be "lead free" with a composition of 95% tin (Sn) & 5% Antimony (Sb) could this be used for bullet manufacture? Seems to be a soft enough composition and is pretty easy to melt. I don't know about the density properties and trajectory issues.......but steel shot has been used for a good while now and I've found it to be pretty accurate. I don't know - just throwing it out there.....
I think winchester was doing that a while back in some 22LR. It was possibly marketed to Kalifornians that are under harsher restrictions?
I think tin is about 5 times more expensive than lead too making it not very cost efficient.