As one who has hunted buffalo with the 1903 Mannlicher Schoenauer, both successfully and unsuccessfully, I must point out that the 6.5x54 is a wonderful killer and always out-performs its terminal ballistics on game with the 160-grainer, however I concur that the cartridge has NO margin for error on buff and therefore cannot be recommended.

Hit in a vital spot, the biggest bull will soon topple, however many years ago, a young bull which failed to drop to the shot was tracked for about 2 kms till the blood-trail ran out, and another km or so till his tracks met up with the rest of the herd. No doubt he's still wandering around out there somewhere. There was a bit of long grass, maybe the bullet deflected slightly, but I'm making excuses....

Nowadays, I prefer to hit 'em fairly hard!