There's a great deal of reliance on temporary wound channels to get the job done, if you judge it by those tests.
Even more importantly...
If you have to shoot to defend your life, what's easier to explain in court: the run of the mill .45 ACP firing 3 rounds, killing the bad guy or the "cop-killer FiveseveN using military style armor piercing ammunition" where you fired 22 rounds into the guy?
Just look at how many gun enthusiasts were mistaken in this thread alone about 5.7 ammunition. Heck, the CC magazine was even testing the rumor. What do you think an ignorant "jury of your peers" is going to think about the 5.7?
Legal liability aside, you risk your life carrying something like a FiveseveN as your primary defense weapon. Just look at the gelatin tests on that website:
If you examine the permanent wound channel, you have essentially a 0.376" diameter 9.6" deep channel. This is indeed adequate penetration, but the diameter of the permanent wound channel leaves a great deal to be desired. Even with the best gelatin results indicating a 0.376" dia. x 9.6" deep wound channel, that's only11.34 square inches of surface area he's bleeding from and that's in a best case scenario too.
The same site lists some tests done with the .45 ACP. Even using the least desirable gelatin results from that site, you get 0.659" dia. and 10.9" penetration. (from a Glock 30 with a 3.8" barrel fired into bare gelatin). That results in 22.56 square inches of surface area he's bleeding from. Again, this is worst-case scenario.Other ammunition tested showed much better penetration andexpansion. (16" penetration at 0.75" diameter, for example).
I'd feel much safer carrying a .45 ACP that will double the surface area of the wound channel (and more than double the volume). Granted, without proper shot placement you're still relying on the bad guy to bleed out, but that happens quite a bit faster when he's got a bigger hole to bleed from.
The goal of defensive shooting is to positively end the threat to your life. Waiting for the bad guy to bleed to death out of a 0.376" diameter hole isn't exactly good for your health. You can not safely rely on tumbling to accomplish the wound channel damage you need. Only two of the four shotsfrom the FiveseveN indicated tumbling occurred.Tumbling is a random event that you can't depend on when your life is at risk. Who cares if you can carry 25+ rounds of ammunition. If you have to use all of it to stop someone, "self-defense" might behard to justify.