I have been casting my own bullets for muzzle loader use as well as modern pistol and revolver use since the early 70's. With the exception of muzzle loader use, for which the lead needs to be pure, there are various alloys from Lymans #2 (ideal alloy for modern bullets) down to wheel weights (semi hard) / lynotype (very hard). The main difference being weight. The harder the alloy, the lighter it is. So a .451 dia. Keith bullet cast in pure lead will weigh somewhat heavier than the same bullet cast in lynotype. As for furnaces to melt the lead in, a bottom pour is the easiest and safest way to go. Lyman made a good one, and Lee made a so-so one. There may be more out there to choose from, but I'm still using my 30 yr.+ old Lyman. Flux your lead while in the pot at temperature with bees wax, found at most drug stores. Tallow (animal fat) can be used also, and it does a good job, but it smells bad. Fluxing will bring any impurities to the top where you can skim them off. Always preheat your molds, and I usually dicard the first several castings until the mold comes to temp. Above all wear Goggles, safety glasses will do, but goggles give the best protection to your eyes, along with heat resistant gloves, a leather apron if possible, and shoes and clothing which completely cover. Molten lead will stick to your skin or clothing like glue if it gets on you. Plenty of ventilation is a must, and this is not to be done in the house or near small children. Also all lead needs to be kept away from little ones who may ingest it from fingers, etc. after handling the lead. This all sounds like alot, but the results can and are to me very rewarding. Oh yea, as for a supplier of lead, other than wheel weights, most any junk yard or plumbing supply house would do the trick.