Its a parts per million thing. It only takes a very small amount of zinc to ruin your lead. The parts per million is very very low. What happens is when you start to cast the lead will not fill out the mold all the way. You will be dropping bullets that look like they were cast from a cold mold. Thats why everyone says to do them in small batches. say you are making ingots out of wheel weights. you should only do about 20lbs at a time. that way you have control of whats going on and in. If you have a batch of wheel weights that look a little funny in the pot. Then you of course flux it skim it flux it again. Then you notice when you pour the ingots they dont fill out all the way. corner edges are round edges. just dont look right. Continue casting ingots with that pot until empty. Then after it all cools down, clean out the pot with warm water and detergent. This is after they cool down all the way. Do the same with the molds and ladels. As for the lead you just poured. Well. Sell it post it on ebay or something in the fishing section. It may make horrible bullets but for fishing weights, jigs it will work just fine. As for shooting. Nope it will be unbalanced Jus flawed. I mean if you want you can still shoot them but your accuracy will suffer for sure.
