To kill a Cape Buffalo, any number of shots to the head will not
suffice. To drop one:

1. Always go for a heart or lung shot from the side.
2. If one is charging you, get out of its way, it will run past you.
Follow it with your gun while it goes past you. It will stop and spin
broadside for a short time. While it is broadside – shoot! This is the
only way to drop it.