I would try Alaskan Bullet Works Kodiak Bonded Core .458" 405 grain bullets over a charge of 55 grains of H322 in Winchester brass with CCI200 primers (appropriately worked up to of course).

Starline brass is unnecessary as Winchester brass has been tested to 70,000 PSI without failure. Hence, its the firearm that is the limiting factor, not the brass.

You learn something new everyday whether you want to or not.