I have only seen three American buffalo taken, one with a .45-90 and a cast bullets weighing close to 600 grains, one with a .375 H&H with handloaded 300-grain Nosler Partitions, and one with a .270 Winchester and a 130-grain Barnes Triple-Shock.
Heart-lung shots were used on all three. Only the bison taken with the .270 was killed with one shot, and it also went down quicker than the other two.
I knocked mine down, one shot, from a 375H&H using a 270grain gran slam.
In hindsight, i didn't need that much rifle. My partner used a 300H&H, one shot, down, another guy used a 338/06.
I can't afford that kind of hunt now but if to do it again probably would default to a lighter caliber and proper shot placement, i.e. right behind the ear if possible.
