imported post
I used to carry .45acp. Let me explain why I carry 9mm. Once upon a time, I worked in the night club industry. The club I worked at was in a bad part of town, and attracted a gangsta element that frequently flashed guns and not so frequently fired them (although it did happen from time to time). Our club didn't serve alcohol, so our bouncers carried concealed firearms, and there were a couple of them that wore vests. I wasn't a bouncer, but I carried a Sig P220 (carried 7+1 in the gun, and 7 more in a spare mag) anyway.
One night, a gangsta decided that he had "beef" with some of the rival gangstas in our parking lot. I saw people yelling and running across the parking lot back toward the club, followed by this gangsta, who was holding what looked like a Mac-11 with a 30-something round magazine. The group of about 30 people was crowded together and cornered at the end of the parking lot, while this guy proceded to yell at them in gansta-ese. I saw this all happening, but he hadn't seen me. I was about 15-20 yards away. I took cover behind a mini-van, puting the front axel between me and the potential shooter, and took aim (side-note, trijicons were very nice in this dimmly lit parking lot, but not necessary). I saw the bouncers stacking up against a wall, guns drawn, but it didn't appear to me that they had any intention of coming around the wall unless they absolutely had to (as in the guy starts shooting).
For several reasons,I didn't take the shot. First of all, I had to get an immediately disabling shot, such as a headshot, since I didn't want him to react by emptying his machine pistol into the crowd. I didn't trust the accuracy of 45acp to accomplish this from this range. Now this is probably just my perception of the round, not it's actual characteristics. Second, there was an SUV full of people behind me, and if I ended up missing and the guy enganged me in a firefight, they would almost certainly be victims of it. And finally, there were about 5 guys standing 25 yards away from me, behind the shooter, who were obvously his fellow gangstas. I didn't know if they were armed, and I didn't want to be stuck in a shootout with 6 people and only have 15 rounds total.
Fast-forward to now. I carry a 9mm which I trust to place a hydrashok in a skull at 15-20 yards, and I carry enough ammo to engage 6 targets. I am much more confident in my abilities with a 9mm, having shot both. I also now know the value of a carbine, although I've yet to buy one. My rifle will do fine for now.
Another side note: I told this story to a british guy and he told me that I should have shot the gun out of his hand. I laughed at the thought, because a Mac11 fires from an open bolt. Putting a hole in the wrong place couldn't be a good thing.