YOU CAN'T DETERMINE BULLET DIAMETER FROM A WOUND IN SOFT TISSUE.
Agreed, but that's not even close to what I said. What I said was "Expanding projectiles create very different wound tracks and wounding effects from non-expanding projectiles even when the final diameter of the two rounds is quite similar. "
I've seen extensive damage outside of expanded bullet diameter many times well below the 2000fps threshold that everybody wants to draw a line in the sand at.
Yes, there can definitely be damage as the result of temporary cavity.
1. If you define damage as bloodshot tissue. The temporary cavity is roughly equivalent to blunt trauma and can cause bruising/bloodshot tissue.
2. If the tissue involved is inelastic and can not stretch/rebound. Under those circumstances the tissue breaks and tears. A lot of the body is elastic tissue, but organs like the brain, spleen, liver, and kidneys, to name a few, are inelastic and can be damaged by temporary cavity.
The problem is that temporary cavity, below some threshold (I'm not going to be dogmatic about 2000fps being that threshold since it seems unlikely that something magic happens at the round number of 2000) becomes an UNRELIABLE wounding mechanism. Sometimes it makes a difference, sometimes it doesn't. And as you get lower and lower below the threshold it becomes more and more unreliable until it's hardly worth talking about as a wounding mechanism at all. I don't know where that happens.
But even when it's not much of a wounding mechanism, it still seems to be effective in terms of "giving notice" to the shootee that he's been injured. Which is important given that psychological stops are so prevalent.
At one point the FBI thought the 10MM was the answer.
IMO, at one point the FBI was in a bind and had to come up with a reason why a number of their ostensibly well-armed and well trained agents were massacred by one man with a rifle and a lot of determination. Blaming the caliber was a good reason and they went with it.
What was the first thing they did after they chose their barnburner caliber? Downloaded it to something a lot more comparable to what they had been carrying than what the caliber was in the beginning. That should tell you something right there.
Using the 9MM as the benchmark for lowest power acceptable...
Penetration with premium expanding ammo is the benchmark, not the caliber.
...declaring it and all calibers more powerful (or bigger, or whatever) functionally equivalent...
Not ALL calibers, just the calibers that fall into the performance range of the common service pistol calibers. And it's not that they're "declared" to be functionally equivalent, it's that no one, in spite of tremendous effort expenditure, has been able to show that they're not functionally equivalent.
You may say that's a fine distinction, but not when you look at it from the proper perspective. If you're making a caliber selection, you don't start off by assuming that there's a practically significant difference across your candidate range, you start off by trying to find evidence that there is. Otherwise you end up making your choice based on your initial assumption rather than letting than the evidence lead you to your choice.
...and then noting recoil as a negative...
Recoil is one penalty you pay with a heavier/larger caliber, but it's not the only one by any means. One needs to look at all the effects and weigh them all against each other rather than focusing on just one, or just a couple of them.
When the bullet technology improves and the .380 is adequate will we all switch to it?
Perhaps. If you want my honest opinion (and I'm going to pretend you do because I don't want you to miss out
), the FBI explanation that what makes the service pistol calibers all perform very similarly in terminal performance is the improvement in bullet technology is just grasping at straws for a way to rationalize why they've done an about face in the course of a few decades.
In my opinion, and based on the evidence I've been able to find, the service pistol calibers have always been very similar in performance when used with similar ammunition. That's been true all along just as it's true that the reason that the FBI switched away from 9mm really had very little to do with bullet performance in the first place.
Yes, bullet performance has improved, but, IMO, that's just a convenient explanation for a fact that was true even before they made the switch to 10mm and then to .40S&W.
I think it's (.380ACP) adequate now with the right ammo!
If you look at Ellifritz's data, it's hard to argue that it's not. The main thing that keeps the experts from recommending it is that you can't get it to reliably penetrate to the FBI's penetration threshold with expanding ammo.
