I've used a ton of wheel weights over the 45+ years I've cast bullets for my Sharps .50/140, I've never had a problem. Steel floats up after the melt. I skim it and the cross off. Then skim the dross off one more time. I put. Small cube of soap in after the second skim, and mix it in good. Then I start pouring to heat up my mold. After about 5 pours, the mold is hot enough to pour a complete flawless bullet. I add back in the partial bullets from first pours, mix well, and pour until I'm done. Any extra I have in my left furnace, I make small ingots. It's easy, but you can get burned if you screw up.