.416 Rigby. Rigby built rifles in that caliber on M98 Mauser actions. There was a pretty famous hunter, who some of you may have heard of, named Harry Selby who used one for around 40 years, shooting it enough to have to have it rebarreled once because it was "shot out". I cannot imagine someone like him using, or some firm like Rigby, producing such a gun if it was not safe. Remember, though, he used mostly factory ammo in it, loaded to the standard load of 400 grains at 2350 fps. Some people like to "hotrod" it and try for that 2600fps or so. At that constant level, the action may not be safe after hundreds, thousands, whatever, rounds, but that is on the handloader. Sort of like having a nice Royal Grade .577 H&H double and seeing how much velocity you will get just because you have the case capacity. My guess, it would be ruined far quicker than pushing a M98 to high velocity/big bore.
Personally, I would not hesitate to shoot a M98 in .416 Rigby (I think Harry's rifle is still being used), or .404 Jeffrey or .375 H&H or any other cartridge of that length. IMHO.