Check out he Cast Bullits Forum. Short answer however is, not worth doing yourself. Just buy them from Bullet Barn, Jet or whatever. Gas check if you want to shoot 1900 fops and faster, 25 Brinnel no gas check for slower. I shoot a lot of Bullet Barn cast in 38-55 and 45-70, plus 30 caliber.
Pretty good accuracy and way cheaper to plink with. They sell .430 240 grain Flat Point for 90 bucks for 500. They will custom swage to .428-.435 for a small charge and you can get gas checks for them. Not worth making them yourself.
http://www.thebulletbarn.com/bullets-lead.html