http://www.nzha.co.nz/wp-content/uploads/2015/08/CastBullets-s.pdf http://www.nzha.co.nz/wp-content/uploads/2015/08/NRA-Cast-Sup1.pdf I like the Lee 20-pound furnace, and I like Aluminum molds, but the latter need lubrication on locator pins and certain other places. If you don't use an appropriate lube on the wear points you get an adhesive wear mechanism called Galling. Lee's recommendation of using bullet lubricant is a bad idea. At the Cast Boolits website I learned of using synthetic 2-cycle oil, which works great. Very small amounts are necessary, and try to keep it out of the cavities. Lead bullets shoot better when shoved into the rifling a little, which supports the bullet on firing, and prevents slumping of the bullet on firing, which gives poor accuracy. Pushing the bullet into the rifling a lot with a semi-auto may give you slam-fires, which may ruin your day. Tin makes casting go a lot better, as it increases fluidity of the Lead, but by itself it does not harden the Lead much. In combination with Arsenic or Antimony, it can harden Lead a lot, especially if you drop the bullet from the mold into a 5-gallon bucket of water. I like to do this not just to get a harder bullet, but also because I don't want a lot of hot-and-therefore-soft bullets around me that can ding each other or burn me. Lead metallurgy is really odd in that cold work of a bullet can produce a softer bullet than one as-cast, so try to have a mold that is going to drop a bullet at the diameter you want to shoot it. Zinc in your Lead will ruin your day. Zinc has a melting point slightly higher than Lead, so if there is any chance there is any in your scrap, you would do well to start with a pool of known Lead at a temperature below the melt point of Zinc, and feed carefully dried scrap in, piece by piece. Most Lead batteries are also a problem now, apparently evolving nasty War gas on melting.