I have just finished reading this whole thread again. It is a great discussion.
I now have a new way of summarizing how I have come to choose a bullet and calibre for cape buffalo.
My approach is a bit different than some of the above. It's just my way.
First, my buffalo killing experience changed for me when I got past the .375HH, and I experimented with the .500 and bigger in a single shot. Obviously this called for me to do some new thinking for one shot kills.
What bullet and calibre would quickly drop cape buffalo, DRT ( Dead Right There)? Let's say "DRT" means that with a bullet in the boiler room, the buffalo goes down within 20 yds..... usually. I like to take the first shot at 50 yds. That probably means .458 cal. or bigger. For me I have landed on a minimum of .500 cal. or bigger for one shot DRT kills on cape buffalo. That's just me!
The quality and design of dangerous game bullets has evolved a lot in the last 15 years. That means that some of the statements above are getting outdated. Expectations of bullet terminal performance risen. Some of these new bullets really out-perform the older designs.
What I want in a DG bullet.
1. A bullet is better if it does not tumble inside the animal.
2. A bullet should have straight and deep penetration inside the animal even if it hits bone.
3. A large and permanent wound channel is possible with some of the new solids.
For me, these are simple criteria that make a big difference in how far a cape buffalo will travel after the first shot in the shoulder. Most bullets don't do all three of these things well.
I like the CEB Safari Solid, it's much superior to the old round nose solid. My favourite "soft" bullets which include expanding and semi-expanding are NorthFork, CEB Raptors and Peregrine BushMasters. No doubt there are other excellent bullets that I will never get to try. I am 81 now and coming to the end of my buffalo hunting. Just one more hunt... Arnhem Land, Northern Territory, Australia, for a management hunt on Asiatic Buffalo! Happy Hunting.