Range lead
I have recovered lead from an outdoor range nearby. I sift the dirt with a 1/4" screen, pick out the bullets. Works for cheap lead, HOWEVER - NEVER put any of this type of lead into a hot pot of lead. You are just asking for trouble with moisture causing molten lead to fly everywhere.
I only start with a cold lead pot, heat up, skim the trash off, bottom pour the lead into ingots. Mostly pure lead this way, but it does have some alloy. The benefit doing it this way is I am far away from the lead pot while it gets up to temp, and the moisture has a chance to just boil off before the lead gets molten. I still don't trust jacketed bullets 100% to not hold any moisture.
Between the unknown composition of the lead you get and the moisture, I think it's better to just buy soft lead, and alloy it if you want harder lead with some solder or linotype, known materials. Range lead is okay if you have to, but for the savings, it might not be worthwhile. That's what I found out, and I never had any problem with molten lead exploding, that right there takes the fun out of it, and could make it very expensive to you if you start a fire or get burned with hot lead spatters. Hot lead can start a fire in tinder. Ingots don't have moisture inside them, if they are solid. Same with lead sheet.