Many years ago in my (relative) youth I decided to salvage lead from several batteries. It was a mess! I did drain the acid first so that sort of minimized the chances burning my face off. Plus, I apparently was lucky. Then there was the fact that the end product didn't shoot very well. I suppose if you have industrial level safeguards the danger is not so great.
My local recycler will give me $5 for a battery (if not needed for core charge). The $5 will buy me 6 lbs of lead so........ Funny thing, I once checked with him if he had any lead i could buy. He says "sure come take a look". He walked me behind the shop and introduced me to a piece of lead that was about 3' X 3' and over 6" thick.
I would have bought it but getting it home was more than I wanted to attempt.