I can't tell if you are being serious, inflection on the internet and all that. But:
Per Gunworks at 1,000 yards a 140 gr A-Max 6.5 creedmoore bullet is moving at 1,554 fps, (one of the better BC available). Most others are going slower.
https://www.gunwerks.com/blog/long-range-pursuit-2/post/the-6-5-creedmoor-9
Per Balistics 101 website a 140 grain Federal Vital-shock .357 Magnum bullet is going 1,400 fps.
http://www.ballistics101.com/357_magnum.php
So you're advocating shooting a cape buffalo with a cartridge just over a .357 Magnum?
Beside the fact that cape buffalo have 2 inch wide 3/4 inch thick ribs and thick bodied. I doubt that with those ballistics you could completely penetrate one lung let alone both of them.
I just do not understand your statement.