Frank Ettin, I agree with most of your points.
There are, however, a few other means of physiologically incapacitating an attacker that do not require hypovolemic shock from blood loss, major skeletal damage, or permanent CNS injury.
One I mentioned. A head shot that does not penetrate the cranial cavity and causes no significant intracranial injury but renders the attacker unconscious.
A penetrating or perforating chest wound may not result in sufficient blood loss to cause hypotension, but may create a tension pneumothorax as a result of perforated lung tissue and/or a sucking chest wound. A tension pneumothorax can cause central circulatory collapse in the absence of significant blood loss as a result of compromise of blood return to the heart. A tension pneumothorax would not likely be immediately incapacitating, however.
Penetrating trauma to the heart does not always result in massive blood loss, surprisingly. The interlaced muscle fibers of the myocardium will sometimes seal smaller perforating injuries before enormous blood loss occurs. Bleeding into the pericardial sac can, however, result in pericardial tamponade, basically shutting off blood return to the heart through external pressure. Peicardial tamponade can develop quite quickly.
Penetrating trauma that severs a major peripheral nerve or nerve trunk going to the dominant upper extremity may functionally incapacitate an armed attacker in the absence of great blood loss or skeletal damage.
While I agree that insofar as handgun projectiles are concerned, secondary wound cavity does not result in any significant injury, penetrating or perforating cranial injuries are different. The soft tissues of the body are generally elastic and rebound from cavitation without sustaining significant injury but brain tissue is inelastic and is significantly damaged by the cavitation/secondary wound channel effect. There are other mechanisms of injury that come into play. Projectiles that penetrate the skull are often subjected to early fragmentation and yaw. They frequently produce secondary missiles in the form of bone fragments detached from the interior of the skull at the point of penetration or exit. And penetrating gunshot wounds of the brain that do not completely perforate may result in a projectile ricochet off the opposite side of the skull.
If anyone doubts the ability of a .22 caliber handgun to kill, study the case of Trooper Mark Coates. Trooper Coates shot his assailant 5 times center mass at a range of around 2 yards with a .357 Magnum revolver but was killed by a .22 caliber projectile that penetrated his heart. His attacker survived. There is a video that shows the shooting and gives an accurate indication of how long it takes for someone with a .22 caliber penetrating heart wound to go down. This video graphically shows a real fatal shooting, so don't watch it if that sort of thing offends or otherwise bothers you:
http://www.youtube.com/watch?v=2FraE77l4fI
