When looking for lead be sure and look for pure lead. A lot of times people will have mixed lead. For black powder projectiles pure lead is the only way to go. Check plumber supply houses in your area. They often times carry "plumber's lead" (or at least used to).

Another place is salvage yards. Here is where they will give you the mixed stuff. I ordered some from a salvage/recycle yard once and it came as old bullets. Well we all know old bullets are not pure lead. There was copper in there, and tin, and goodness knows what else. They got a little upset when I refused to buy it stating they had bought it for me. I explained what I was needing it for.

A friend doing me a favor dropped off some lead pipe. It was so full of crud inside from years of service doing something I would rather not talk about, I have not used it yet. This is last resort lead...

I have been ordering pure 99% (at least) lead from MidSouth Shooters Supply on line. This is lead is so pure you do not even need to flux it most of the time. It is a 5 BHN from what I understand. When you order it you might as well order the #30 pound amount. It gets used up a lot faster then you think, and the shipping will kill you in most cases.

I cast my own round ball, and conicals, and have so for years. The projectiles I cast out of pure lead I have noticed are much more likely to expand when they hit something hard then the ones other people cast or I buy. I shot some 533 grain conicals a person casted. They were shot into a pine log. You would think they would be flat. Not so, I swear they are almost good enough to load again. He claimed they were cast out of pure lead. I also shot some of mine and they were so deformed you had a hard time telling what they actually were.

That white crud on your bullets means you need to get out there and shoot more... I make up hundreds of conicals at a time and as long as you do not pre lube them they stay fine.