Posted by
Deaf Smith:
Pick the most powerful cartridge you can control and carry.
As has been discussed, "control" is relative and variable, and
everyone can better control a lighter-recoiling firearm in faster fire than a harder recoiling firearm. That's basic physics.
...good shot placement tends to stop better.
Of course, and that is an understatement. It has been recognized for decades that hitting something vital is essential to effect a physical stop.
The problem is that in a deadly force incident, " good shot placement" means hitting something vital, and because the vital parts are internal, that's not something that one can ensure with a good sight picture. It is the result of a number of things, not the least of which is luck. Put another way, it is the outcome of a stochastic process.
One bullet that goes into the upper chest area at a particular point, from whatever angle around whatever axis, my hit something vital, or it may not. Change either the point of the entry wound slightly or the angle slightly and the situation may be different.
And yes, it is easier to make one or two good hits in a short time with a powerful weapon than it is to make 5 or 6 good hits in a short time with a less powerful weapon.
One "good hit" might suffice, and two would be better.
However, we have to define "good hits" as
hits on the small, vital internal parts of the body, and we cannot know precisely where any of those parts really when they are hidden inside a three dimensional human body, and hitting them when they are moving is even more difficult. Therefore, making that one "good hit" is really something of a matter of luck, and making two requires more luck.
It is not really all that likely that one or two shots that hit the body will turn out to be "good hits." That's a matter of luck, and that luck can be improved markedly by shooting more rounds.
Of course, one has only so much time to do it.
None of that is new. The need to hit vital parts of the body to effect a physical stop was discussed at length in Urey Patrick's report in 1987. The report then analyzed the human body and presented some conclusions regarding penetration requirements, which incidentally, have not changed. They led to the widespread adoption of handguns chambered for the .40 S&W cartridge, which, in premium defensive loadings, met the penetration requirements.
What has changed in recent years is the fact that there are now several premium defensive loadings in 9MM Parabellum that also meet the penetration requirement. These came about as the result of advances in bullet technology.
The lower recoil impulse of the 9MM enable shooters--all of them, no matter how practiced--to shoot controlled stings faster.
That's not new.
But combined with the new fact of better consistent penetration with reliably expanding bullets, the lower recoil impulse gives the defender--any defender--a better chance of hitting those small vital parts within the body.
And
that is what constitutes "good hits."
And that, and nothing about the "basic common denominator", is the reason for the recommendation. If it were just a matter of the average skill level, we would find experts such as Rob Pincus carrying more powerful rounds--which, incidentally, he once did.
Nothing that I have said in the forgoing was not already addressed, at least to to some extent, in the link in the OP and in the two links I have provided to Rob Pincus' recommendations.
The vast majority of experts do seem to be leaning toward the nine today.
