When loaded with quality JHP bullets, 9x19, .40, and .45 have very similar capabilities in regards to stopping people.
In regards to penetration, that is entirely dependent on the bullet and the load. FMJ and CMJ bullets will penetrate more than JHP, SWC, and RN bullets. Generally, velocity holds more influence than mass on penetration; allowing with all things equal (bullet type) the 9mm to penetrate more. For the purposes of use on people, anything over 15'' of penetration in ballistic gelatin is a waste of kinetic energy, thus why JHP bullets exist. JHP's allow you a better transfer of KE, along with a larger permanent wound channel, to the target.
As far as that Officer's department's reasoning...they're full of crap. My defensive, carry, and competition weapons are all 9mm and I feel very comfortable with it. .40 and .45ACP are good choices as well, although you are compromising on capacity with the .45ACP.
9mm is more capable than most people give it. The military is largely responsible for this with our use of FMJ ammunition, which is a terrible match for the 9mm cartridge in regards to stopping a person.
It all boils down to "you do your part, it will do its" with any service caliber handgun.
Last edited by Trigger
on January 3rd, 2009, 6:15 pm, edited 1 time in total.
"A golf course is the willful and deliberate misuse of a perfectly good rifle range." - Lt. Col. Jeff Cooper (ret).