For many years the .30/338 was THE 1,000yd precision cartridge. More neck and better case performance than the straight .300win mag...
The .338/300win offers more flexibility than the straight .338 case. Have loaded 79gr of XMR 4350 with 250gr Sierra bullet as a max and started out with 65gr of same powder as beginning load... Gets you right there with .340wby and .33 Dakota... Much greater flexibility than the larger ctgs though.
Might be able to simply improve your present barrel to .338/300 and get a new throat, unless it is really shot out and crocodiled as happens with stainless.
Might get a new .476 bolt body, if Kimber would sell you one... The 6.5/284 will keep up with 7mm Rem and others. The 284win case is great for wildcatting up to .375 bore. .30-06 and .30/284 share same data for loading, so you got ballistic and handloading twin but shorter case, more room for seating longrange bullets.
.264win is also still a great performer. If looking to shoot 200gr bullets or heavier from a .30cal, the .30-06 AI will really deliver and give you 5rds in the magazine, also the .338-06AI is a great performer with heavier bullets.
