It has been said by some that no caliber will drop a ambushed Buff to the ground on the first shot --
375H&H-nope, 458WM better, 470 NE-more better!---

But PH Kevin Robertson notes that his 505 Gibbs, 525gr Woodleigh soft has put Big Buff on the ground first shot x 3 buff in his book THE PERFECT SHOT-AFRICA.

It then seems that 500+ cal, ie the 500 Jeffery, 500 AHR, 505 Gibbs, 500 NE, and larger calibers should have what it takes also.

If shootable, are the 500's the minimum way to go?

Is this hype or fact? Is there a better minimum choice??