I think your both right. There's more than one way to skin a cat.
MCgunner said:
It's about energy on target. Energy is equal to one half mass times velocity squared. .45" is only 0.10" bigger than .35" (numbers rounded to 1/100th inch.)
If all that mattered were the hole, I'd shoot a cross bow.
To GeorgeDuz and McGunner:
I think you're both correct.
I think 4 things matter: Accuracy, size of hole, energy dumped in target, and momentum. i.e. - your both correct.
The .45 ACP relies on accuracy, size of hole, and momentum. Works well.
The .357M relies on accuracy and energy dump. Works well. Same with 9mm, but the 9mm has less to work with, but is still adequate.
The .40 relies on a combination of all in equal proportions and is my preference for stopping potential combined with small enough diameter for lots of ammo.
All these cartridges above get it done very effectively with the right ammo choice.
The problem with both the 9x18 and .38 Spl is that they lack diameter so must rely on as much velocity as they can get. The 9x18 is also hobbled by the fact that it can't go very fast. i.e. - the 9x18 isn't all that powerful. I think the best you can do with 9x18 is whatever heaviest JHP that goes 1050 fps from muzzle. Then shoot accurate. With .38 regular pressure, I'd say the same.
However, with +P Corbon 110 gr JHP 1250 fps muzzle the .38 Spl with 4" barrel then kicks butt, in my opinion. A 3" barrel is also respectable with this ammo. Same with other supersonic 110 and 115 gr JHPs, which are probably +P. This is almost 9mm Para performance.
For 9x18, I'd recommend the heaviest JHP that will go approx 1050 fps from muzzle. Why? See
http://www.thehighroad.org/showthread.php?t=181798
For both .38 Spl, I'd recommend the heaviest JHP that will go 1210 fps or faster from muzzle. That's going to be a +P 110 or 115 gr bullet. Why 1210 fps or faster? See
http://www.thehighroad.org/showthread.php?t=181798
Note your energy equation is correct. Nothing to add there.
Momentum is mass x velocity.
A .45 ACP doesn't have much energy, but it has loads of momentum combined with a big diameter. There's more than one way to get it done and velocity and energy are one of several options. The large momentum option seems to work well only with large diameter bullets.
By the way, a crossbow is VERY deadly and I think has plenty of stopping power. The problem is you can't conceal a crossbow.
Regarding momentum as a stopper: If a person hit you with a brick, it would have large diameter and lots of momentum, but not much energy. You'd be "stopped" cold. On the other hand, a tiny piece of supersonic shrapnel can "stop" you in your tracks too. Either approach has proven stopping power, as long as you have enough of it. You just have to have enough of either or a good combination of both (like .40 cal has both).
i.e. - subsonic bullets only have a good stopping power record when combined with large diameter heavy JHP or Semi-Wadcutter bullets.
If your bullet is small (like 9mm), then you NEED high velocity to get it done. This is why heavy subsonic 9mm JHP bullets have a poor stopping power record, but lighter supersonic (above 1210 fps muzzle) 9mm JHP bullets have a good stopping record. The 9mm lacks diameter, but with a light, fast, supersonic bullet makes up for small diameter with high velocity and energy.
Stopping power statistics based on real shootings support the above.