No this will be a bit more cerebral I think...or hope...for you the reader.
Doing a little research on stopping power tonight for a couple different projects and I kept coming up with all of this data on power, penetration and stopping power ....but what about factors? Factors, in the Huey's Gun Book (if ever published) are the things that a bullet or projectile must affect in order to effectively stop your opponent....
- Psychological. Does shooting your adversary break his will to fight? There are many stories about determined (or drugged) individuals taking multiple rounds of what should be "one stop shot" caliber weapons and being able to fight back. Many of our Medal of Honor winners have citations telling tales of men mortally wounded but able to kill many others before they expired. Other stories exist of 6'5" 250lb brutes curling up in a ball and crying for mercy at the mere appearance of a weapon. A small puncture wound has sometimes forced the onset of shock in gunshot victims and taken them out of the fight, permanently. Sure, I imagine 80%+ of the population will be dissuaded by the mere presence of a firearm and probably 95%+ will just sit down and quit if shot at all, but you need to keep those outlying variables in the back of your mind...just in case. Thankfully, in my vision of how it is, just putting a round on target takes care of 95%+ of your assailants.
- Structural. Ever seen anyone unfortunate to break their pelvic girdle? Luckily I have no first had knowledge of the injury. From what I gather its very painful and can prevent a person from using their lower extremities entirely. The same can be said for injuries to other major bone and muscle structures in the body...somebody shot in the shoulder with a shattered humorous or clavicle will most likely not be able to use that arm. The wounds may be grisly and painful, but not necessarily fatal to the individual shot unless not properly attended to. A wound such this inflicted by a firearm, say shooting somebody's legs and shattering a knee, will most likely immobilize your target and more importantly, get you into that zone where you psychologically break them before you have to ultimately take them down.
- Cardiovascular Collapse. This is the most often worried about damage caused by a firearm, bleeding out (Exsanguination) or dying from lack of oxygenation of the blood (hypoxia) due to lung damage. It is usually the most deadly form of injury that can be treated to avoid death if the proper knowledge and materials are available and also the most common type of injury caused by projectiles. Basically, you destroy internal life essential organs when you shoot someone that cause the targets blood to drain out, cause a collapse of the lungs and inability of the body to oxygenate the blood and ultimately lead to brain death caused by lack of oxygen delivered to it. This can take from few seconds to several minuted depending on the injury sustained. It most often will directly lead to shock, which is a life threatening condition in and of itself.
- Central Nervous System Damage. Just like zombies, humans will generally stop moving around and trying to kill you if shot in the brain. Death is normally the result of a transecting brain injury (penetration involving both hemispheres) or that of the cerebral cortex. Just being shot in the old melon normally isn't good in any situation. There are many famous cases of people surviving after being shot in the head (James Brady and Gabrielle Giffords more recently being the most high profile) but these cases are generally the exception, rather than the rule. In addition any shot placement to the central nervous system in the spinal cord will normally result in either instant death or permanent paralysis of the target, depending on how high up the spinal column the shot hits.
Of course, there are many times when one or more of these factors are involved when stopping an aggressor at the same time. Somebody may be shot in the thigh which breaks his femur causing him to become immobile, nicks his femoral artery putting him at cardiovascular risk and also breaks his psychological will to fight at the same time. So while a lot of time and effort is put into determining the "perfect" round for self defense, I think its important to more accurately describe what the round must do to stop an opponent rather than just casually muse that "this +P+ HP round with Vulture Claws will totally shred him...". Many rounds will affect these factors, and they all don't start with a "4" either folks...
This article was not meant to be a guide for stopping an opponent, nor a "target list" of what to aim at when engaging a threat. I continue to stress in my training that shot placement is important and center mass of a normal human silhouette not only gives you an aiming point easiest to acquire on a target but also just happens to put many of these factors into play at the same time. I am offering this information as an insight on my personal philosophy and not as any type of training advice. Please use your head when venturing armed into the world. Too many people arm themselves it seems without taking the time to understand not only why they are arming themselves, the legalities involved in this behavior or the mechanics of what is involved in the process of doing it. God knows I still have much to learn myself. I do know this though, the number one way to stop an opponent is not to get yourself into a situation where you need to engage them in the first place. Be smart out there folks.