h-m,
I wouldn't be too quick to pitch those joints. They are likely made of "wiping solder", which is a varying mixture of lead & tin; usually around a 50/50 mix. They would be an easy source of tin, to make your bullets fill out better. Just mix up a small batch & try it.
Bill,
The place I have seen lead pipe used the most has been in the drains of places like high school & college chemistry labs, photo developing shops, industrial labs, etc. It was used extensively. for chemical-type drains, before PVC came into vogue. I do have a dim, childhood memory of some plumbers working at my grandparents house, and setting/sealing the joints of cast iron pipe with lead.