Four pounds of pure lead to 1 pound of the mix. That would take the 10% of tin and Antimony and divide over 5 pounds of lead. 10 divided by 5 = 2. So you would have 2% tin and animony in each of the five pounds of cast lead. This still is much harder than pure lead, and should be used with conicals, or knowing that the round balls cast will be slightly lighter in weight, larger in diameter, and almost certain to not expand on hitting animal flesh. Adjust your sights, adjust the patch thickness, and be prepared for greater penetration, but less reaction by deer and other game when they are hit with this alloy ball.
I would recommend adding 9-12 lbs. and reducing the percentages to 1 percent or less per pound. But that is just MHO. The softer the lead, the better performance you get from a RB.
Why not just set that lead aside and use it to cast bullets for rifles, and modern handguns? Or trade it to some caster who does reload modern cartridge guns?? Its worth money to any caster, and if you can get your money out of it, you can buy scrap pure lead at your local junkyard.
