At close range and high impact velocities, fragmenting bullets are susceptible to failure.
I'm curious about what you mean by your statement above, in particular, what you mean by 'failure'. Are you saying that in such close range, high velocity impacts the bullets 'fail' by expanding too rapidly, or that they fail to expand?
Noel asks an interesting question, one that I think many people would answer differently. Most shooters agree on what merits of external
ballistics are desirable (minimize drop and wind deflection, maximize energy, etc). However, I'm learning that there is a lot of disagreement about what terminal
effects are 'desirable'. The spectrum goes from shooters who want 100% weight retention, no bullet deformation and max penetration, to the other extreme being rapid expansion and fragmentation.
Of course, as phorwath points out, the 'ideal' terminal bullet performance probably depends on the kind of animal, how it's oriented, and where you hit it.
Even in the high end academic papers I've turned up about bullet lethality, there is much disagreement among the scientists about what attributes of terminal bullet performance are most lethal. Every model that tries to 'rank' bullet lethality according to some parameters (energy, momentum, velocity, etc) is contested by some 'expert'. Turns out death is not easy to calculate.
So I'm interested in responses to Noels question as well. What do you, hunters, consider to be 'ideal' terminal bullet performance? How much does it depend on the details of the shot?