NitroX:
To answer your query on my calibre choices for buff:

When I first moved to the Northern territory from North Queensland a couple of decades ago, I had Vic Pedersen build me a .416 Taylor on a 98 Mauser, with which I took my first buffalo hunting alone on foot. An interest in nitro-express doubles, which I had secretly entertained for some time, now had an outlet and I started acquiring examples as finances allowed. My first double was a 20/.577 Express which accounted for a number of good bulls. Almost all of the buffalo I have taken since those early days have fallen to double rifles, most to my .400 Jeffery.

I also like to hunt pigs and donks with my 6.5 Mannlicher Schoenauer carbine, and had it in my hands for two buffalo encounters, the first of which concluded favourably. The second resulted in a long tracking job, which concluded unsuccessfully when the animal rejoined a mob and his tracks could no longer be identified. I believe he survived. Dunno what happened, there was plenty of long grass, a deflection perhaps? Who knows. No room for error with that cartridge. I would quite happily hunt buffalo again with the 6.5, a little more cautiously perhaps, but can't see the point when there are better choices in my gunsafe.

I certainly wouldn't recommend the 6.5 MS to others for buffalo under any circumstances.