I always thought that the 458 Winchester Magnum launched a 500gn projectile at 2,150fps.

But, I've been rummaging around and I'm just not seeing that. eg. Winchester currently lists a 510gn at 2050fps (and that's asking the bloke selling it to you).

Question 1:

What actual performance can be expected from a 458Win?

It is SAAMI rated to 53,000 CUP, but that would be for a bolt gun, would you go that hard in a DR? Pedersoli back their Kodiak to Malin 1895 levels (~45,000 CUP?), thats a big step down.

Question 2:

What performance level could you resonably expect to load the 458Win to in a DR?

AR2201

ps. assume 500gn projectiles out of 24" barrels