My solution, which John Buhmiller and I arrived at separately, was to cut the .460 Weatherby case down to 2.50" and neck the remaining case to .500-.505" (I did one of each). This allowed the loaded round to feed through the M1917 magazine box I fitted to my P-14 actions with no modifications. We both felt the full sized .460 case was too long and had excess case capacity.
My cartridge has just enough shoulder to make it feed easily.

The resulting case holds 90 grains of 4064 up to the base of the bullet and duplicates .500 Nitro Express velocities in a 22" barrel producing 2150 fps with a 570 grain bullet. If you PM me your email address, I can send you pictures of the rifle and cartridge.