I was gonna ask the same thing, WHY?
If you want a flatter shooting rifle get a .375H&H, if you want more power get a .458 Lott.
I believe it was Asquare who believed the ideal bullet velocity was 2400fps, for max penetration. In fact I believe his ammo is loaded to get close to this speed.
So no reason for a 400gr bullet @ 2400fps to go faster IMO.
Get yourself a .416Wby if you really want a fast .416...but again see no reason to go faster, either go bigger for power, ie .458, or goto a .375 if you want faster/flatter.