I have used partitions on elk moose deer and bear and have never seen one fail at any velocity.I have killed elk and moose with 140 gr partitions at 3500 fps out of my 7mmstw and they exited in all but one case where about 60% of the bullets weight was retained on a lengthwise shot on an elk.Accuracy has only been in the 1-1/2" range which is not up to my standards but they have never come apart even at high velocity and close range.