The NRA tells us that every year there are approximately 2 million
incidents where people use guns for self defense. In 96% of these
incidents shots are not necessary because of the intimidation value
of the gun.
When shots are necessary, about two thirds of the remaining 4%
stop voluntarily. Maybe they were not even hit. Maybe they were
hit but it did not cause a deadly wound. Whatever the cause, they
don't want to get shot at again, so they run, or stop and surrender.
The remaining approximately 1.36% is our main concern. Up to this
point the lowly .22 can, and does, fill the bill. But when the S.H.T.F.
we need to stop the attack.
It’s all about assessing your risk, right? There’s something like 225 million adults in the US. Using your numbers from the NRA, that would mean there’s a .01% (1x10e-4) chance in any year of being in a circumstance that a .22 might not work. That doen’t factor in any skew that occurs due to people’s bad lifestyles choices (people that buy illegal drugs, etc.) or the crime rate where people live. I don’t carry a .22, but even a .22 improves your odds a lot.
These posts pretty well nail it and it's why both armed citizens and police officers get away with carrying and even shooting firearms that they in no way shoot effectively in a real world shoot.
If you already shoot an Airweight .38 badly, carrying a .22 LR that you shoot better isn't much if any of a handicap.
And that's the irony I see in the arguments in this thread. Shot badly, no handgun cartridge is significantly more effective than any other, but most of the time you just need a handgun that is "good enough". It goes like this:
1) carry a concealed handgun, and you may start displaying better situational awareness and/or appear less afraid in the face of an approaching threat and your odds of avoiding a life threatening situation increase, even though the gun is never even drawn.
2) Draw a gun in the face of an imminent threat and a competent petty street criminal will do what he or she is trained to do - turn and run to avoid getting shot - and your odds of getting killed or injured again decrease because a gun is present, even if you never fire it.
3) If you shoot it and miss, a fair percentage of assailants will turn and run because they are facing an armed victim who is actively shooting at them, even if they are shooting badly.
4) If you do have to shoot and hit your assailant - anywhere - the statistics are pretty clear that about half the time the assailant will stop the assault once he or she has been shot, in order to avoid being shot again.
5) However, in that other half of self defense shoot, you're going to need to keep shooting until the assailant is down.
6) If he or she is also armed with a hand gun you'll need to shoot effectively while receiving fire, which will produce a great deal of stress and your shooting will need to be second nature as there will be no mental bandwidth available to focus on any thing you have not completely mastered.
6 1/2) This should include the ability to move away from the attacker and toward cover.
7) If the assailant is armed with a knife or blunt object, then you again need to know how to move to get off the X, how to create space to employ a handgun, and how to retain and shoot a handgun from a close in retention position.
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In 1 through 4 above, it doesn't matter what you carry. Anything is better than nothing.
In 5 and 6 above, if you learn to shoot the way I described above, you are covered. Here, what you shoot matters but what matters more is that you start with a handgun that fits you well and doesn't cause you to develop a flinch or other bad habit. You can always move to a more effective cartridge later once you've mastered the basics.
In 6 1/2 and 7 it matters a great deal what you carry as you need to be able to shoot it well and you need a cartridge with good terminal performance. However 6 1/6 and 7 also require another skill set that blends the use of a handgun with movement, and with other self defense techniques.
You'll note I never discussed focusing on a tactical reload, as a reload is almost never required in an armed citizen self defense shoot. That said, it's not a big deal to add it to your training. Make every reload, including administrative reloads, a tactical reload. If you practice once a day you'll get 365 repetitions per year. Practice 3 times each day an you'd have over a 1000 reps a year, and you'll start to get good at it under stress.
If you carry a revolver learn how to reload it quickly using a speed loader and the FBI, Universal or Stress Fire methods. There are pros and cons to each.
The FBI reload is fastest, but it was designed for revolvers with full length ejector rods shooting .38 Special, it has reliability issues with short ejector rod revolvers (barrels less than 3 inches, and with the longer and often sticky .357 Magnum cases.
The Stress Fire reload is a bit slower, but it works with DA revolver with a swing out crane, and with sticky .357 Magnum cases.
The Universal reload is a bit of a hybrid. It's slightly slower but much more reliable than the FBI reload. It's also slightly faster and slightly less reliable than the Stress Fire reload.
All of these methods use the strong hand to manipulate the speed loader, and it should be carried on the strong hand side.