I see you have mentioned something about using battery lead.Stay away from battery lead.Most battery's now days use calcium in there lead and does not mix and cast very well.also if you use wheel weights,watch for the presents of zinc in some weights.When melting down the weights keep the temps low because lead will melt before the zinc will and you will be able to remove it along with the clips.
For more info and advice about casting bullets,go to
www.castbulletassoc.com
I have read and have tried using a peice of lead free solder in the pot.This will provide better casting because of the tin in the solder.This was used in my w/w mix.