Even properly made tactical body armor won’t stop a bullet if it’s not used correctly. All of the following situations have occurred and have lost lives. You can get into trouble...
...if the strike face is flipped
There’s a reason the strike face is identified as the strike face. That’s the side that the bullet is intended to hit, and it’s designed for that specific job.
When the bullet hits, the energy is dispersed across the panel, but there is still an impact point pushing part of the panel against your skin. Panels are tested not only by strike face performance but also by this backface deformation. The back is designed to protect your soft tissue, and though you will get a nasty bruise, it’s doing its job.
Flipping the plate makes the wrong side do the wrong job, and in this case it’s much more likely to fail.
...if you underestimate your assailant’s weaponry.
There are times when you know exactly what you’re up against...you’ve either seen the threat or reconnaissance has told you exactly what’s in their hand. Maybe soft armor is what you need to improve your mobility if a hand-to-hand situation arrises.
But if you enter a situation where you could be up against anything, you’re going to need a higher rating of armor. Going up against guerrillas you’re going to run into a lot of Kalashnikovs. When in doubt, always wear tactical body armor that can stop rifle rounds.
...if you just wear the carrier.
If you think the carrier is going to stop anything, you’re mistaken. People aren’t going to stop shooting at you just because they think you’re wearing plates. Vest looks cool (our vests look really cool), but don’t put yourself in a situation where you can’t get to the plates before the action starts.
Also, always wear the front and back panels. The movies always show the bad guy screaming a taunt so that you’ll face him. In real life they will shoot you in the back while you’re having a conversation.
...if you’re likely to get stabbed.
If you’ve gotten into a situation where firearms aren’t the main concern, make sure you know the limits of what you’re wearing. Some vests offer better protection than others against knives. When things get stabby, make sure you’re wearing the right vest.
...if you’re not wearing it.
This might seem obvious, but it won’t help you if it’s in the back seat and you’re in the front. Put it on before you get to the scene, because the shooting might start before you’re out of the car.