Could use any of the .378 Wby based cartridges. I like the idea of shortening the .460 Wby (or .416 Wby) down to 2.5" and form it to .416. It should be easy just use a pipe cutter and cut to length and then size the case.

Something like this.....
https://www.lowes.com/pd/BrassCraft-1-4-in-to-1-1-8-in-Copper-Tube-Cutter/999904025

Life Member SCI
Life Member DSC
Member New Mexico Shooting Sports Association

Take your responsibilities seriously, never yourself-Ken Howell

Proper bullet placement + sufficient penetration = quick, clean kill. Finn Aagard

Ken