We use to cast battery acid into Fishing weights but I believe it repelled the fish due to the "flavor". I do not know of any problems, health or otherwise, associated with melting it down in some thirty years, however, we were careful not to breath the fumes. I have several fisherman friends who still make their own lead weights from batteries. I would be careful to make sure all the "acid" or harmful metals have been removed as it might effect the metal of the gun.
Becareful!!

Currently own two Morgan cars. Starting on Black Powder hunting to advoid the mob of riflemen.