I really think you need a new rifle in this case, 416 Weatherby! 400gr@2700fps!

Think it would have to be a custom if you didn't want it to be a weatherby.

Anytime I've read anything about the 416wby on african game guys seem to love it, favorite cartridge, always 1 shot kills etc..., course the kick/muzzle blast etc... is hard to deal with.