One of the big factors almost all of the PHs I've discussed buffalo bullets with in the past 20 years or so is that many feel some of today's expanding bullets can penetrate TOO much, potentially exiting and hitting another buffalo in a herd. This is exactly what happened with a good friend of mine on his first buffalo hunt. He used a small-maker "premium" 400-grain expanding bullet in a warmly loaded .45-70 (I can't remember the brand, but it's in my notes somewhere), and shot a good bull broadside--which expired pretty quickly after it ran into some thick brush.
But after they followed up the bull, one of the trackers informed them that he'd found more blood, beyond where the bull had been standing. They followed the blood, and found a dead cow--which luckily had also been hit broadside through the chest. It could just as easily been gutshot, or somewhere around the edges.
Which is why several PH's I've talked to recommend the 270-grain Barnes TSX for buffalo, rather than the 300-grain, which tends to exit, especially on broadside shots. This is one of the virtues of A-Frames, and some other bonded bullets: They expand so widely they often stop under the hide on the far side--which is exactly what happened when a hunting partner shot a bull with a 400-grain AF from a .416 Remington Magnum about 15 years ago. The bull went only 40 yards before dropping, and the bullet was found on the other side of the ribcage, under the hide.
I remember Brian Pearce killed 2 Cape Buffalo with 1 shot from a 45-70 with l believe was Buffalo Bore ammo and thought it was a 400 grain solid
