It was designed for double guns to match Rigby's 400 gr .416 bullets at 2400 fps but at much lower pressure. The case is hell-for-stout and in a strong action it should not be difficult to get another 150-200 fps. It ought to make a 300 gr 375 really fly.

Geez, that 500-416 is sure a beautiful case. Necked to 375 and rechambered Ruger #1....
ROAAARRRR! Somebody do this please. And the #1 can handle at least 40k.

[chk LAR, gatcha.]

There you go. Done and done.
OR..., just leave it at 416!