The 300 WM will achieve 1000 yards and more.

Is there a specific goal you are trying to accomplish that requires a specific cartridge? Like a goal of reaching beyond 1000 yards as inexpensively as possible? Or reaching 1000 yards and more with an obscure cartridge?

As someone else posted, there are plenty of barrel makers.

To change barrels you'll need at least an action vice, go and no-go gauges, and a barrel nut wrench. Some people get by without an action vice. They use a padded vice instead. Some people take the opportunity to replace the factory recoil lug and barrel nut when they install a new barrel.

Good luck. Sounds like a fun project.