A lot of gun owners worry about their gun going “click” instead of “bang” when they really need it. With basic maintenance and using good self-defense (i.e. jacketed hollow-point) ammunition, the vast majority of modern handguns are incredibly reliable. As long as you test fire your gun and ammo combination on a relatively regular basis, you’ll have little cause for concern.
That said, the desire to reduce the odds of a mechanical malfunction is perfectly understandable. The single most likely cause of failure: the ammunition magazine.
The usual justification for carrying a spare ammunition magazine: more rounds! Fair enough, but given that the questionable old maxim that the average gunfight is three rounds in three seconds at three yards, there’s an even more important reason to carry a spare: you need a Plan B if Magazine A fails.
That’s why so many manufacturers spend so much time and money creating reliable magazines. It’s also why the aftermarket for high-quality magazines is so robust. Gun and magazine makers know gun owners don’t ever want to have to use a Plan B. It’s also why many knowledgeable gun buyers examine the sturdiness of a gun’s magazines when making their firearms selection.
Yes, it’s that important. Even so, excrement happens. Magazine feed lips (the top of the magazine) can get bent or dinged. Dirt and other foreign substances find their way into magazines. Springs eventually lose their springiness. In short, your ammunition magazine is much more likely to fail than your gun.
To hedge against a magazine failure, examine them on a regular basis. Look for foreign substances; make sure your mags are both clean and functional. Check for bent feed lips, or any other damage. If a mag loads and unloads well, the slide locks back when empty and shoots reliably, you should be good to go. But you need to shoot them to know.
It’s worth repeating: the gun range is best place to check your magazine/ammunition combination.
If you experience a magazine-related failures, try other similar magazines. If there’s a problem with one mag — where your other, similarly loaded magazines don’t fail — don’t carry the non-operational mag. (Mark it with an X on the bottom with a white Sharpie and set it aside to use for failure drills.) If all of your magazines fail, change your ammo. If that doesn’t solve your problem, consult a gunsmith.
More than that, carry a spare magazine and practice on-the-fly mag changes, including changing mags while you’re moving. You can do that at home with empty magazines and a safety-checked, unloaded firearm. There are magazine holders and clips of various sorts, both for your pocket and your belt. They make carrying a spare easy. Use one.
Bottom line: carry an extra ammunition magazine and train with it. Your life may depend on it.