Reliability Does Not Mean "It Works"

Let's dive into why your gun can work fine, and still be unreliable. It's a bit paradoxical, so bear with me.

The concept of reliability is basically "what is the chance the gun will not cycle correctly next time I fire." (You could imagine other problems, like a mag suddenly becoming stuck or the stock falling off or something, but let's stick with firing right now.)

The intuitive approach is to use the past as an indicator for the future - if the gun has always worked before, surely it will work next time too. Unfortunately, this isn't always the case. Consider the rifle below, which was sent to the School of the American Rifle (SOTAR) for inspection.

During the course of the inspection, some small marks on the chamber stood out. This isn't a very visible problem - the gun had always run fine, and surely some little marks on the chamber aren't a big deal, right?

The ultimate issue was that the barrel wasn't aligned correctly, which caused the bolt to impact it - hard - every time the rifle fired. This will seem fine, for a little while, but before too long it will cause the bolt to break. If you're only putting a few thousand rounds per year through the gun, you might not have that problem for a while - months, maybe even a year or two. And yet, this is clearly an issue!

This is just one example, but I'm using it to illustrate the underlying point: plenty of things that seem to work fine are actually just problems that haven't gotten big yet. Your personal experience is not "the truth" in every case! We have to rely on data and people who specialize in this area, because our own experiences might make something seem fine when it isn't.

The place where people go wrong is to assume that the past always predicts the future - if the gun worked before, it will keep working next time. But this is only true on a small scale, because each time you pull the trigger a small, imperceptible problem could be getting just a little bit worse. There are two ways that we can "see" these problems:

• gather data for a large number of cases, then draw conclusions - the rifle above is from PSA, which doesn't have a stellar reputation for quality control and will therefore have lower reliability compared to a more carefully built gun
• understand the system well enough to draw conclusions from an in-depth analysis, such as the tiny markings in the example above

Importantly, relying on the data approach means you have to have a whole set of test cases - the only way to say things like "1 in 5 guns from this manufacturer fail after 5000 rounds" is to test a double-digit number of guns from them for thousands of rounds each. For the system understanding approach, you need an expert - someone who has the ability to measure and verify the gun to rule out known issues. Even then, the way that known issues arise is from past experience - it's just that the past experience is turned into measurable indicators ("there are markings on the chamber, so the barrel is misaligned") rather than statistics ("lots of barrels are misaligned from this manufacturer, so this one likely is").

Reliability is critical for a defensive tool. The way to evaluate reliability is not "does the gun go bang" but by looking at failure rates, statistics, and technical data such as known indicators and failure cases. A gun that has worked every single time in the past may still be unreliable - you just might not know it yet!