If the old fishing sinkers are pure lead they will work just fine. But are you sure you want to waste them? Lead is getting expensive to purchase. Not only has the price of metal gone sky high but as you are aware, so has shipping been on the increase.

If you have a source for lead, that is the best. Any one you know does roofing? Ask them if they ever come across lead sheeting for valleys and flashing. Also plumbers get lead pipe from time to time still in old houses and when water pipes are torn up. While this is dirty lead, it is able to be cleaned and still used.

So if you have a source for lead, then all you need is the molds, melting pot, ladel, skimmer, bees wax, mold lube, heat source, and make a dump box. Lee makes a nice .530 mold that can get you started. I do not think they make a .570 mold but they do make a .575 mold.