I've heard this myth repeated for years, by supposedly knowledgeable people. I heard it again today at a gun show, a woman was looking to buy a concealed carry weapon, and the salesman was telling her not to even look at the .380acp's because they where ineffective for defense, and she'd probably be safer using a BB-gun or pepper spray! I couldn't hold my tongue any more, and disagreed. The guy literally told me to shut-up, because I didn't know what I was talking about, he teaches gun safety classes, and he's an expert! I did my best not to laugh in his face as I walked away snickering.
Granted I'm no expert like this guy!, but..... If 25+ years of professional nursing have taught me anything, it's to respect the damage any gun can do! When I got home, I looked over some recent chrono data I did for my hand loads and factory ammo, and estimated the foot pounds of energy they produce, starting with my BB-gun, and going up through my .45acp.
My pellet rifle, will propel a .177cal 8gr pellet at 530 fps, to produce roughly 5 foot pounds of energy.
My .22lr does 1050fps with a 40gr bullet, to produce 97 foot pounds of energy.
My .380acp propelled a 95gr bullet, at around 900fps, to produce 171 foot pounds of energy.
My .38 Spl. load does roughly 800fps with a 147gr Moly bullet out of my 1 7/8" barreled 340pd, to produce 209 foot pounds of energy.
My 9mm does 1050fps with 125gr bullet, to produce roughly 306 foot pounds of energy.
The .357 Magnum load I recently tried in my 340pd averaged 1069fps with 147gr moly bullet, to produce 373 foot pounds of energy.
My .40 S&W does roughly 900fps with a 185gr bullet, to produce 333 foot pounds of energy.
My .45acp target load uses a 200gr moly bullet at 830fps to produce 306 foot pounds of energy, and my full power defense load firs a 230gr JHP, at 900fps, to produce 413 foot pounds of energy.
So, in summery, the .380acp produced roughly 34 times as much energy as my BB-gun! Almost twice as much energy as a .22lr. 82% as much energy as my .38spl, and 42% as much energy as full power .45acp! And I can attest first hand that it has more than enough power to disable, and/or kill someone, because I've personally pronounced patients dead who had been shot with one.