I've seen many people debunk the Marshall and Sanow One-shot-stop statistics. But I think some people miss the salient point with their work. I agree that no handgun can be expected to have a 94% chance of stopping any assailant with one shot somewhere to the body. But I must say the Marshall and Sanow findings are extremely useful because they numerically compare effectiveness of different rounds in real-world encounters. (I realize there are valid questions about the statistics they used, that's for another discussion)
It should not be discounted that the relative effectiveness of the different calibers is entirely pertinent to the discussion of self defense. What I mean is this: Marshall and Sanow's findings show 90% effectiveness for one caliber and 40% effectiveness for another smaller caliber from real-world encounters. For me, it's simple. I want the 90% caliber. Does this mean I can expect 9 out of 10 assailants to fall with one shot? No. Does it mean this round is likely MUCH more effective than the smaller one? Yes.
In my psychotherapy practice, I know that certain techniques work well with, say, abuse victims. I don't care whether it's 90% effective or 80% effective. I'm going to choose said treatment over one that shows 50% effectiveness with such a client.
I believe Marshall and Sanow has great significance as long as it's used properly.
My $.02.
I agree with you and I think Evan Marshall agrees with you. That's how I see it, a comparative guide to the relative effectiveness of different loads. Now, you will notice most of the nay sayers are big bullet worshipers at the church of the 1911, pastors Jeff Cooper and Chuck Taylor. They so despise the unholy 9mm that they refuse to admit that it's even in the same percentage range as the holy caliber. Some even refuse the power of the .357, but many will concede the point since it's a revolver and nobody serious about self defense would carry anything, but a 1911 after all...
Rather than believe statistics of actual shootings, the pastors of the holy church make up books for their bible containing their proven formulae of "stopping power", which of course are based on momentum being that is the strong suit, the only strength of heavy and slow since it is linear in relation to velocity. They present these truths as handed down by God, just in case you don't believe them, God's initials quite coincidently being "J C".
Well, I know there's more to terminal ballistics than any silly momentum equation given proper torso hits and seems to me, knowing what I do about statistics and statistical inference, that the real world is the best reflection of what works. You can say all you want about the holy implement being "proven in war for a century", but give me some statistics to PROVE it! After all, the primary weapon in war is the long arm. The side arm is only an officer's decoration to be actually used in either very special circumstances or in sheer desperation. I know I'd never personally want to go into actual combat armed only with a handgun.
And, also, I'm not restricted to hardball. I don't give a flip about Geneva or Hague.
There is plenty missing IMHO in the understanding of physicists as to what happens when bullet meets bone and flesh. There's lots of variables and no simple momentum formula explains anything. That's almost as bad as trying to build a climate/weather model with a single variable algebraic equation.
Until all is known about terminal ballistics, the best measure I can find for how one caliber relates to another is the stats.
Now, it really isn't too complicated if you don't have some sort of agenda to prove. It really is common sense. You got your major caliber guns and your minor ones. .38, 9, .40, .45 example of some of the more powerful defensive loads, make good energy and still controllable. Then, you got your .32s and your .22s and your .25s. I mean, like Kinky says, how hard can it be? The only fence sitter I see in the line up is .380. To me, it's a compromise, currently a necessary evil if I need to pocket carry. That's really all I need to know about caliber performance, carry a caliber that makes 70% or better preferably 80% or better in the M/S stats and go with it. .380 barely makes that cut. Don't expect it do kill 70% of the time on the first shot, so keep firing until it works. That's about the size of it, way I see it. If you like .45, fine, but you're only kidding yourself if you think you can take on a bad guy armed with a 9 and the sheer superiority of your bullet's momentum is going to win the day for you. If the bad guy gets off the first accurate shot, your widow is likely to be collecting her life insurance.