I'm pretty sure that all round ball molds are sized to work with pure lead. That is, the "shrink factor" they used to figure out the right size for the cavity was the one for pure lead.
Other alloys of lead have different shrink factors so they might shrink more or less than pure lead does when it solidifies so, if an alloy is used, it will make a ball that is slightly different in size.
Of course, the lead temperature when it is poured can also have an effect on how much the lead shrinks too.
Other alloys of lead have different shrink factors so they might shrink more or less than pure lead does when it solidifies so, if an alloy is used, it will make a ball that is slightly different in size.
Of course, the lead temperature when it is poured can also have an effect on how much the lead shrinks too.
