I have heard that wheel weight lead is not a real great thing to use
for balls, but this is uncomfirmed. When I need lead for either my
Pennsylvania .50, my Brown Bess .75, or my 1841 Mississippi, I go to
our local shooting range and dig it up. I wash it off,then let it dry
(water and molten lead are a dangerous combination!), and then melt
down the bullets in an old iron ladle. When rendered down, I can pour
off the molten lead into homemade ingot molds, and save them for later
casting. I usually trash the old copper jackets from the melted down
bullets, as I can find no useage for them.
It saves money, and just takes a little elbow grease to keep my
flintlocks supplied with lead.

Hope this helps some,
Keith