Go to the Cast Lead Bullet Association web site:
http://www.castbulletassoc.org/index.shtml
Their members have been casting, experimenting, developing, competing, hunting, etc. with cast lead rifle bullets for many, many years. They are the authority on the subject.
This is the other good cast bullet site:
http://castboolits.gunloads.com/
Between the two sites you will be very busy.