I have recently purchased a P.O. Ackley rifle in .460 Ackley Improved. This is based on a Model400 Brevex magnum mauser action. Heavy ported 26 inch barrel. What is the parent cartridge and how are cases made? What might this gun be worth as I am considering sale or trade? Stock is fairly radical design, nothing fancy, but solid.

460? I'm assuming it's a 460 Wby with 40o shoulder angles. His more famous would be a Lott blown out with slight shoulders.

Did you mean 450 Ackley?

Barrel is stamped Brevex-Ackley .460 Improved

Sounds like a chamber cast may be in order.