FWIW, a friend and I went on a bison "hunt" (shoot would actually be more descriptive) this past Saturday. He was using a .338/.284 loaded with handload 210 Partitions at 2650 fps. He fired 3 shots, and we recovered one....retained weight was 192 grains, and expansion was excellent. The other two shots, at about 50 yards, were complete pass throughs.
I was using my .270 Win with handload 160 grain Partitions at 2850 fps. I, too, fired 3 shots, and recovered one bullet. The front end wiped away completely, (normal with the Partition at hi-velocity) but the petals and shank remained intact and penetrated from the left rear ribcage, diagonally through the entire chest cavity, blew through the far ribcage, and came to rest under the hide. Retained weight of this bullet was 91 grains. Though the offside shoulder wasn't actually touched by the bullet itself, there was a substantial amount of bruising to that shoulder from the impact force. The exit wound through the offside ribcage was almost fist-sized, but the bullet ran out of steam at that point, and didn't exit the hide.
The other two shots I fired were clean through-and-throughs through the ribcage. Range was ~90 yards. The buffs weighed ~800 lbs.
I've pretty much decided that against really large game, the bullet construction is more important than the chambering. I saw one buff take four chest hits from a .300 Win Mag at 50 yards, and it displayed very little reaction to the hits...until it fell down a full minute after the last shot. Turned out, he was shooting plain old Rem CoreLockts, and his penetration was a little less than stellar. Not a one exited the animal.
If I do this again next year (I haven't decided on that...one "meat cow" is a lot of meat), I have some 150 grain Swift A-Frames I'll try out and see how they compare against the Partition. I suspect they'd retain a lot more weight than did my Partitions, but, OTOH, the Partitions worked as well as anything out there, and better than most.
Mike
edit: There was a wide variety of chamberings in play that day. Given proper bullet construction, chambering really isn't of paramount importance. But....the important thing is to have plenty of sharp knives, and good sharpening equipment. Skinning and butchering 3 buff in an afternoon is a pretty tall job, and you go through knife edges like crazy.
