I have found most of mine at ranges. Indoor ranges will let you come in after hours so long as you promise not to sue them for cancer, most of the time. If you do the indoor range thing, a respirator is a necessity, a painter's suit is better. If you are outside, you can usually just pluck them off the ground. If you start "mining" or digging/sifting outside, the same precautions as inside should be taken.
It is very expensive for ranges to have their lead cleaned up by professionals so most are more than happy to have some guy or gal come in and scoop their bills away.
THIS^^^^
I belong to a gun-club with an indoor range. The backstop hadn't been mined for a very long time. I got a friend who had a bunch of kids/gang he could enlist for free labor, so we mined the pit one night. (The pit is the sand trap at the bottom of the 45 degree steel plates the bullets hit behind the targets.)
It yielded a ton,(yeah 2,000#'s). It took about 7 20# propane tanks and a couple weeks to re-claim the lead. It varied in hardness, but I've been using it with ½% tin to cast most of the handgun calibers. It runs about 12-14 BHN.
Here's my haul when all was said and done;
Turkey fryer, 10 quart cast iron dutch oven;
Muffin molds, lee and lyman ingot molds, and one that a fabricator guy I know made, casts a 5# ingot.
The other half, kept by the buddy that helped;
This lead was hardly free. Cost of transportation, propane, and sweat. I don't put a dollar cost on my free time. I would not be paid otherwise so it's free.
The best part about casting is being able to control every aspect of what produces an accurate lead boolit load. The alloy, the size, you get to pick the nose shape, the amount and type of lube, and the hardness.
The equipment cost, molds, furnaces/melters, sizers all cost money. But one casting session that produces a couple hundred boolits will pay for most molds. There's a couple of beautiful creations from Slovenia made by Miha Previc that were in the $150.00 range.
Imagine a 500 S&W lead boolit round for 14 cents! I've seen them sell for over 2 bucks apiece. Home cast boolit, surplus powder and a primer that is about 4 cents. Or 45/70 rounds for about the same price!;