I don't think Zinc would fill a small pellet sized mold well.Pewter might work. I melted a lot of pewter down and cast it into .458 bullets. Simply to have a convenient and consist small "ingot" for alloying in lead. They did come out beautifully though...Ps. Elemental lead stays where it lands. It doesn't leach into the environment. The fear mongering of lead on/in the ground is overblown. Lead oxide is indeed a problem, but small lumps of lead have little surface area and therefore produce tiny amounts of lead oxide as they age.