I have two .416s, a Rigby and an upstart Remington Magnum, and I would take both. I would use the Rigby, since I am so hide-bound a traditionalist (within reason, I should add), and pack the Remington Magnum for back up purposes.

With elephant, buff and hippo on license, the .416 would be my preferred minimum.

As for sights, well, I would want irons for the close up stuff with elephant and hippo, but glass for buff, lion and leopard.

So, I would mount my S&B Flash Dot 1.25-4x20mm variable on top, with an Allen wrench in my pocket for more rigid mounts, or with lever-actuated Talley QD mounts. Depending, of course, on whether my CZ actioned .416 Rigby, or my Winchester actioned .416 Remington Magnum, were the rifle at hand.

The only other caliber I might choose would be the .458 Lott. Nice compromise that, for an African DG hunter. Big enough for anything, yet suitable for anything else, at any reasonable range.

And one thing I have learned in my relatively few days afield after African DG is this: Bigger is definitely better.