This info is from the 2009 Lyman bullet making guide. Wheelweights are 95.5% Lead, .5% Tin and 4% Antimony, which makes a bullet hardness of #9 on the hardness scale. The perfect pistol bullet is Lyman No. 2 mix, which is made up from 9 pounds of wheelweights and 1 pound of 50/50 bar solder, (sold at plumbing supply.) Melted together, Lyman #2 mix ends up as 90% Lead, 5% Tin, and 5% Antimony, which on the hardness scale is a #15, making a good bullet. Not too hard, not too soft. Those square, sticky tape backed wheel weights, that are used on some mag wheels are Zink. They will float in the lead pot, won't melt unless you get your lead temp. way too high. Junk em. Hope this helps.
I use 9# wheelweight to 1# 50-50 lead-tin bar solder. Casts well and is hard enough for handgun bullets. Don't try to use the wheelweights that float. They are made of zink. Get them off before they melt.