I've never bothered to form 8x57 brass from something else. Sure, it can be done, but I just bought a few boxes of Remington and Winchester factory 8x57 ammo and shot them up. Voila, brass. When I decided I wanted more but didn't want to buy loaded ammo, I just bought new Remington 8x57 brass from one of the local gun shops. It's not terribly hard to find.
That said, smokinjoe named the 3 I'd have said.