The perfect cape buff rifle for me would be a 500 NE double with 24 inch barrels, ejectors, and open sights.
I don't feel the need to shoot big game at long range, so for me, a scoped rifle is not going to be part of the deal.
If forced to use a bolt gun, I'd feel ok about using a 22 inch barreled 458 Win mag, with crf and open sights of course.