If your looking for top end performance, about the most performance you can get out of that action/bolt face combination, is a .338 edge or edge improved. You will get 2900-3000+fps with a Berger 300 depending on barrel length, powder, node, ect. So do you want the utmost performance or do you want something easier? If you want a repeater in the .338 edge then I would suggest getting a Wyatts 4" mag box and have it fitted to your action as well. Alot of people are loading these to 4" OAL or more. And especially considering the new Berger 329 that will most likely have an absurd BC, I would want a cartridge that could push the heavier bullets coming out.
Something easier and cheaper would be the 338 win mag, but personally, if I had that custom action I would go .338 Edge or possibly Edge Improved.