One additional factor I've read about (but don't remember the reference) but which sounded credible, came from a study conducted during Cape Buffalo culls in S. Africa some years ago. A veterinary pathologist tried to differentiate what happened between chest-shot animals that dropped-right-there, versus same shot that ran-then-died.
During necropsy he reportedly detected evidence of cerebral stroke in animals that dropped/died quickly, and credited that phenomenon to bullet strikes as the moment of peak systolic pressure (heart contraction) rather than at the lower diastolic pressure (heart relaxation). His theory went that when a Cape Buffalo died instantly (or at least was incapacitated instantly) the cause was a pressure spike causing internal brain bleed or profound neurological stunning. And given the impossibility of timing such a shot to cause cerebral stroke, the outcome of each shot was random, and couldn't be perfected (at least not a chest shot).
The "cerebral stroke" theory is interesting, but still unproven. I've discussed this at length with medical colleagues and ballistics experts, and I've done a lot of research myself in reviewing autopsy reports, and so far I've not found any evidence to suggest this is in fact a "real thing". The concept of a remote injury (a bullet wound in the chest) causing a remote injury to the brain is highly suspect.
First thing, you have to define "cerebral stroke". Basically, in any stroke, there is catastrophic disruption of blood flow to the brain. This is very different from traumatic brain injury (TBI) caused by head trauma, explosions, MVA's, concussions, and the like; those are a different animal altogether.
Strokes are categorized as two types, due to 1) interrupted blood flow, either by formation of a clot or by an embolus travelling up the arteries to cause a blockage of a major artery of the brain, or 2) bleeding inside the cranium. Among ballistics people, there is some question of there being a third mechanism, i.e., a pressure wave from a bullet striking the heart causing damage to the brain indirectly, presumably in the manner of a cerebral concussion such as one caused by head trauma. This third mechanism is highly doubtful, and in any case is not really a "stroke"... in theory, it's a type of TBI caused by a spike of internal cranial pressure (ICP), which has so far never been demonstrated in any lab in the world, despite several really good attempts to reproduce it.
In 30+ years of medical and ballistics study, I have been unable to find any definitive evidence in the medical or ballistic literature of a pressure wave being propagated up the fluid column of the arterial system in human or animal bodies. The true physics experts in the ballistics field tell me that this phenomenon is eliminated by the gradual narrowing of the arterial trunks as they branch off into the cerebral circulation, and perhaps moreso by the elasticity of the arterial walls, which have the ability to dampen any pressure waves extremely rapidly.
Now we get to the problem of the apocryphal "African Vet" story. (The African Vet story you has been widely circulated for many years... not sure if they're referring to Dr. Kevin Robertson, but he's sometimes named in the anecdote.) The problem with this story is that in the first type of stroke (ischemic stroke) even an expert pathologist will not be able to identify a stroke on autopsy, whether in the lab or in the field, because the damage is microscopic, not macroscopic. It's often hard to identify even when the stroke is very recent, and you have a CT scanner to work with. The second type of stroke, the hemorrhagic stroke, could be identifiable if it were massive enough, but again it would require careful dissection of the brain and microscopic sections to reach a definitive conclusion. And I don't know of any veterinary pathologists who do brain dissections and microscopic studies in the field, in Africa or in North America.
At this point I'm not saying it can't happen, only that there are a lot of anatomical and physiological reasons to argue against the theory. As such, my hunting is based on an understanding very similar to that of JB in the OP of this thread. In over 50 years of hunting I've learned that if I shoot animals in the manner that JB describes shooting animals, I usually get to take that animal home and eat it.
