Between me and my father, we put 6 cape buffalo in the salt with 400 grain TSX bullets in our .416 Rigbys (carried solids for follow-up). I would hesitate to recommend anything else for a bolt-action rifle for buffalo. If you are wanting to shoot a double, that's a different story (country was too open to bring these out of the case this year).
In a 300 caliber rifle, it's hard to go wrong with Barnes, AccuBonds, or Partitions. If you put it where it needs to go, the trackers will come through on their end of the bargain.
If you are a handloader, give Peregrine Bullets a look. We gave them some field testing in their development and they are a nice bullet.
