Lately I have been hearing that a number of people are carrying their defensive semi-automatics without a round in the chamber. I suppose that this is most often done with a thought to increasing the safety of the handgun and avoiding a negligent discharge. However, it considerably defeats the purpose of the defensive handgun.
A criminal attack often comes from very close range and with very little, if any, warning. A person simply may not have time to chamber a round in his or her pistol before the attacker is upon them. In addition, chambering a cartridge requires the use of both hands at a time when the support hand may be busy trying to fend off the attack or pushing a loved one out of the line of fire. From holster to on-target, one should be able to operate a defensive handgun with only one hand, should that become necessary. 
Some folks are concerned about a single-action semi-automatic having the hammer cocked back. I was too, back in the Dark Ages. But I took the time to get some professional training and learn the pistol. I soon found that they don't go off by themselves.
Others are concerned about the fact that striker-fired pistols—like the Glock—have no external safeties. And they have heard stories about people who have accidentally shot themselves. Well, let me let you in on a little secret ... those are not accidents. They are nearly always a case of negligence—that is, someone fooling with the pistol and causing the trigger to be depressed when they didn't intend for it to be.
In the case with any of the autoloading handguns, a good defensive instructor can teach a person to operate it safely and to carry it with a round in the chamber.
In the case with any of the autoloading handguns, a good defensive instructor can teach a person to operate it safely and to carry it with a round in the chamber. Regardless of those people who think they are a born shooter—Wyatt Earp Jr.—nothing will benefit the defensive shooter like professional training. And proper and safe manipulation of the defensive handgun is an important part of that training.
Regardless, there are those who just don't feel comfortable carrying any sort of semi-auto pistol with a round in the chamber. The solution is a simple one and it has been around for well over 100 years. Of course, I am talking about the double-action revolver. When the DA revolver is fully loaded, no springs are depressed and the hammer is not cocked back, yet it is ready to go at a moment's notice. A person who carries a pistol with an empty chamber is telling the world that they don't know what they are doing. I hope that those folks will get serious about their personal defense, get some professional training, and carry whatever defensive handgun they have confidence in. Whatever gun they choose, it should be ready to go when the attack comes.
