With respect...
Experts who may have shot one or two human beings, ten thousand pieces of paper or a thousand blocks of jello can be over-impressed by '5 inches' or even '10 inches' of penetrative capability.
Others, of whom I am one, have become convinced of the fallacy of 'just enough penetration' theories, through extensive experience in the hunting fields. Theories are wonderful, but the real test is done against flesh and bone.
Human felons are just another species of hyped-up wild animal. Experienced hunters know that you need to break a lot of bone and make a big hole clear through the creature, to stop it quickly.
A human being may, under certain conditions, go down quickly after a hit with a smallbore, but this is a psychological effect. I take my cue from the way Platt kept fighting with multiple non-survivable small-caliber wounds, during the Miami shootout.High velocity smallbores may make nasty wounds in soft tissue, and I certainly wouldn't choose to be shot with one, but it takes mass and momentum to really get the job done through barrier materials or against very determined opponents.
If I have to shoot someone, I want to know that I can shoot clear through Murphy to do it. 'Enough gun' is never enough.
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If they take our guns, I intend to let my hair grow long and acquire the jawbone of an ass.