Hello,

I think that you will have to take one bite in a sour apple:

Factory ammunition available:
416 Remington: high pressure
416 Rigby: magnum length action

404 Jeffery: magnum length action recommended, but pressure is low

I would recommend reloading the 10,75x68:
Fits a 98 standard system, holds 4 cartridges, shoots good bullets from Woodleigh (347grs at 680 m/s) and has not much recoil. Forget Taylors remarks, Harald Wolf had good results upto and including Australian buffaloe with GOOD bullets!
Only drawbacks are cases and prices for reloading tools, but if you want a standard length action, try this one!

Rolf