Many small, easily concealed semi-automatic pistols which are recommended for law enforcement backup or concealed carry use fire .380 ACP or smaller bullets. While these small caliber handgun bullets can produce fatal wounds,they are less likely to produce the rapid incapacitation necessary in law enforcement or self-defence situations.
Handguns chambered in .380 ACP are small, compact, and generally easy to carry. Unfortunately, testing has shown that they offer inadequate performance for self-defense and for law enforcement use whether on duty as a back-up weapon or for off duty carry. The terminal performance of .380 ACP jacketed hollow point (JHP) bullets is often erratic, with inadequate penetration and inconsistent expansion being common problems, while .380 ACP full metal jacket (FMJ) bullets offer adequate penetration, but no expansion. All of the .380 ACP JHP loads we have tested, including CorBon, Hornady, Federal, Remington, Speer, and Winchester exhibited inconsistent, unacceptable terminal performance for law enforcement back-up and off duty self-defense use due to inadequate penetration or inadequate expansion. The use of .380 ACP and smaller caliber weapons is not acceptable for law enforcement use and most knowledgable agencies prohibit their use--based on past experience, to my knowledge none of the agencies you mention currently use .380's.

"Almost everything I've learned about the science of ballistics has come from reading "Street Stoppers" : The Latest Handgun Stopping Power Street Results written collaboratively by Sanow and his co-author, Evan Marshall - Copyright ©1996, published by Paladin Press), said Chisholm.