I've been pondering the post which reccommended melting with a torch, over a piece of steel, and letting the molten pour out as shot into water. --- I've melted lead many times with an acetelene torch and would warn against using one on lead because the flame is so hot that it burns lead and creats a lot of smoke, which sure isn't good for human lungs. Use a propane fired weed burner and the flam is softer with MANY tims as many btu's. This will start melting a wide section of large pieces quite quickly, and pour of lead so fast it's hard to beleive. When melting small scrap one has to stir it if blowing the flame down on it, because trash, like wheel weight clips and whatever else, will lay right where it dumped it load of lead and cover the peices below.
I don't recall whether I mentioned it previously, and am sure not going to read this whole string to be sure, but I cut a lot of lead on a vertical bandsaw using a wood cutting blade. It saws smoothest on large pieces if a strip of lard is smeared on the lead in line with the intended cut. As the saw passes through the lard it picks up enough grease so the chips don't clog and bind. A coarse blase if best. Fine ones will fill with lead and hang up if feed at a good cutting speed. The blades I'm using now are three tooth per inch, on a 3/4 inch wide band.
I happened to be cutting up some scrap lead over the last few days and when I hit some unknown laarge pieces, I sawed off a small chunk which would fit under the LBT hardness tester penetrator to check hardness. I was making push through and rifle throat slugs so the lead had to be very close to pure or dead soft. That trick worked very well and I learned that I had one three foot piece, about 70 pounds which is probably lino or close. Another which has laid on the shop floor near the door for years because it was shiny and very rough, so I didn't care to mess with its unknown character, turned out to be 11 bhn, which is quite hard for a large ingot, indicating it is at least 'bullet metal'.
To be sure of hardness when melting down unknown lead. melt just a little with a propane torch, pour it into a well heated mold, and water drop it. Check the hardness after the cast and again 24 hours later. The two readings will inform you as to what you can do with that particular chunk of lead.
For years I've read of people using dental lead and saying it is pure lead. When a customer sent a bullet cast of it, I did a hardness check and found it to be 11 BHN. Grab up all of it that you can lay hands on. That customer tells me that dentists have to pay a hazardous waste fee to get rid of it and will thank you for hauling it off without costing them. Get all you can lay hands on, even if you have to pay for it. I've heard of a couple dentists who know it has value!