It's About Fighting, Not Just Shooting
Normally we don't talk about rules in self-defense and personal protection with the exception of the Four Rules of Gun Safety, the First Rule of Gunfighting, and your state's Lethal Force laws because everything else is mostly "guidelines".
The First Rule of Gunfighting: Have a gun.
The .22 pistol you have with you is better than the .45 you have at home. True. Yet, we find a lot of time and energy spent on the effectiveness of different handgun calibers compared to others as well as the magical "stopping power "discussion.
We've added our two cents over the continual debate about handgun calibers and the general consensus is basically all handgun calibers are weak sauce compared to more effective rifle bullets.
What we need to focus on is why we are carrying our handgun in the first place -- WE ARE PREPARED FOR A FIGHT. The gun in gunfight is just the modifier. Just like fist in fistfight or knife in knifefight.
It's a fight. And great advice that I got from Rorion Gracie is that fights go the way they want to, not necessarily the way you want to. Remember, the adversary gets a vote in the fight. And there are plenty of street examples of bad guys who have refused to stop after being shot multiple times. Even mortally wounded adversaries have continued to fight back effectively.
Take this example of police officer Tim Gramins' shootout with a bank robbery suspect in Skokie, Ill.
"There were 17 total hits on his body including three fatal shots to his head, a couple to his torso, and one to his abdomen," Gramins says. "Which means that even though [the criminal] was mortally wounded before the head shots, he was still able to engage me. And these rounds were from a .45 caliber Glock."
Multiple hits. From the vaunted .45. And the adversary is still trying to kill the officer. Hey, I love my .45, so this is not meant as a knock, it's an illustration of why you can't count on a handgun caliber to reliably stop a fight instantly. The same article linked to above notes similar examples which are more well-known in shooting circles and law-enforcement training. Perhaps the most notable is the FBI Miami shootout with criminals Platt and Matix.
While Platt and Matix were mortally wounded during the shootout, they were not incapacitated. Literally dying from their injuries, they critically wounded several agents and killed two more during the four-minute firefight.
The video below is a depiction of the shootout which is supposedly a very realistic recreation of the shooting and is reputed to be used as a training aid for many agencies.
This means we need to continue to fight to stop the threat even if our chosen weapon platform has not been successful in the initial clash. We need to gain and maintain tactical superiority. We might do this by:
Improving our position by gaining distance. Take advantage of your firearm by moving farther away from the adversary. Every foot you gain from "the hole" (two-arms length) improves your chances of avoiding hits from handgun fire. And, yes, fight-stopping shots from handguns can be made from surprising distances. Take the example of Air Force Security Officer Andy Brown who made a 70-yard headshot to stop a man who was firing a MAK-90, a Chinese made AK-47, outfitted with a 75 round drum at people on Fairchild Air Force Base. Brown made this shot with a 9mm Beretta M9. If you've ever fired the civilian version Beretta 92F you probably have a better appreciation of Brown's fight-ending shot.
Improving our position by moving to better cover. This means getting behind materials which can stop bullets. This is different from concealment which simply hides you from view of the adversary. If you've not thought about this or been trained to seek cover now is the time. In my experience, former military members seem to have a better base in first seeking cover than civilians and -- sometimes -- even law enforcement officers. On the flip side, use your knowledge of cover versus concealment to continue to engage an adversary who seeks concealment. Below is a very instructive video of two police officers getting into a gunfight with a suspect. There are lots of great lessons from this one incident, but I'm calling it out because the officer who engages the adversary is not hesitant to shoot through the front doors to finally terminate the fight. The bad guy runs out through the doors, but hooks back to pick up his dropped handgun. In this case, the doors have glass panels so the officer can still see the adversary, but the point is he realizes he can shoot through materials in the fight rather than think he needs to go out of the doors for a clear shot.
Improving our position by flanking the adversary. In our context of interpersonal combatives, this means we are moving laterally towards the opponent's sides. We are "getting off the 'X'" to avoid the adversary's main projection of force and forcing the opponent to move to track us and respond to our movement. This concept calls for us to move off at an angle or circle the opponent to find and exploit an opening before they can cover and counterattack. We do this all the time in combatives to open up angles for kicks and strikes or as we take the opponent's back in grappling. In shooting, it's more difficult to track a target moving horizontally than moving directly towards us or away from us. I would use this especially when there is no cover. I personally know an officer who successfully used this to get inside the radius of the bad guy's outstretched gun arm and terminate the shooting. There is at least one popular YouTube personality who poo-poos this strategy. But remember, action always beats reaction.
Targeting the head to shut down his CPU. Placement is power. Even smaller calibers have the capability of shutting down the brain. Much like in striking, hits to the head are usually debilitating to a fighter, both physically and mentally. When you are hitting him in the head at the very least you are physically stunning and scrambling his thought processes. Mentally, there can be a very strong psychological effect here. In the Walmart shooting video above, one of the officers is shot in the face. His immediate reaction is to run away to find cover. He is obviously not thinking clearly and is out of the fight because he has just been shot in the face. Headshots are powerful. However, because the brain is so valuable, the skull can do a remarkable job of protection. There are cases of bullets actually hitting, then skidding off or around the skull. The legendary Jim Cirillo of the NYPD Stakeout Squad describes a case in which a suspect regains consciousness and sits up and starts talking after being shot in the head multiple times with a .38 Special. In the case of the officer above who was shot in the face, thankfully he survived and returned to the force albeit for light duty. To increase our ability to stop the fight more reliably, we train to make more effective hits on the human head. We can do this by concentrating on the area which can be visualized as a band measured by the size and orientation of your ears which encircles the head. This is the area from the top of your eyes to the bottom of your nose extending around your entire head like a band. The head can be a difficult target to hit anyway and confining your shots to just this band could prove to be too time consuming. Fire two shots to the head to increase your chances of making the hit. Many of us have been trained for the classic two shots to the body and one to the head. The math proven by the instructors at PFC Training shows that two shots to the body and two shots to the head is preferable. Despite their difficulty, headshots are a high-percentage fight stopper. The example of the officer I used above on flanking ended the encounter with headshots.
Shoot the attacker until they are no longer a threat. Determined and committed adversaries can be surprisingly resilient and take a remarkable amount of damage while still trying to kill you as we've noted above. Conversely, other attackers can be surprisingly fragile and can stop at the first shot -- even when not actually hit. Your situation is that the bad guy is doing something terrible that leads us to reasonably conclude that we need to stop him right now and nothing else is going to work except for shooting him. Regardless of your defensive handgun caliber, keep hitting him until his behavior changes. If he stops, great. If he runs away, great. But if he continues his homicidal rage, you must pummel him. Until he stops.
Remember, as a civilian, we have no duty to control and arrest the adversary. We are trying to save someone's life by making him stop.
Move from a Shooter to a Gunfighter
All of the above is what leads our training efforts to move from being a shooter to a gunfighter. We have to think hard about our training. At first we need to focus on the very mechanical part of shooting. But our training can't end there. We need to transition from just shooting to fighting with our handgun. We need instruction and coaching in the tactical elements of armed encounters as we transition to gunfighters.
The bottom line is that we have to win the fight. Win the fight. Every time.