With many bullets you will get better penetration at lower velocities vs higher velocities. This is due to the bullet being more prone to fragmentation or overexpansionat high velocity. A friend of mine use to shoot a home cast 255gr 44 cal keith bullet in a sabot out of his non magnum CVA using 80gr of RS. H shot a buck once through the front chest, he found the bullet under the hide between the rear legs about 30" from entry with almost 100% weight retention. Velocity was around 1500 to 1600fps at the muzzle. I think 100gr of powder should be plenty.