The Truth About FMJ Rounds, Defensive Handgun Use, and Body Armor
There’s a lot of confusion out there about how full metal jacket (FMJ) rounds work against body armor. Some think FMJ bullets of any kind can punch right through armor, but that’s not exactly true. The truth is, whether a bullet gets through body armor has more to do with the power and speed of the round than just the bullet’s design. To understand why, you need to understand what FMJ rounds were actually made for, how body armor is rated, and why rifle rounds pack a much bigger punch.
History and Purpose of FMJ rounds
FMJ bullets have been around since the late 1800s. Back then, shooters had problems with lead bullets fouling their barrels, which made their guns less accurate and harder to clean. The solution was to cover the soft lead cores of those bullets with a harder metal jacket—hence the name full metal jacket. These reduced fouling and made guns more accurate.
FMJ rounds also became the standard military cartridge after the Hague Convention of 1899, which banned expanding bullets in war. These rounds kept their shape better when they hit a target, making them reliable for deep penetration. However, FMJ rounds were never made to beat body armor.
How Does the NIJ Rate Body Armor?
Body armor gets tested and rated by the National Institute of Justice (NIJ) to see what kinds of bullets it can stop. Here’s a quick look at the levels:
- Level IIA and II: (Older categories) Protect against common handgun rounds like 9mm FMJ and .40 S&W.
- Level IIIA: Stops higher-velocity handgun rounds, like .357 SIG and .44 Magnum.
- Level III: defeats rifle rounds up to 7.62x51mm NATO FMJ.
- Level IV: The toughest—can stop armor-piercing rifle rounds like .30-06 AP.
When it comes to handgun-rated armor (Level IIIA and below), rifle FMJ rounds are a real problem because they’re faster and hit harder. But even big handgun FMJ rounds, like the .44 Magnum, usually won’t get through Level IIIA armor.
Rifle Rounds
Rifle rounds pack substantially more energy than handgun rounds.
- A standard 9mm FMJ handgun round hits with about 350 foot-pounds of energy.
- A .44 Magnum FMJ handgun round punches out around 1,000 foot-pounds.
- A 5.56x45mm NATO rifle round? Over 1,200 foot-pounds.
- A 7.62x51mm NATO round? A massive 2,500+ foot-pounds.
That extra energy and speed make rifle bullets much more dangerous to body armor. In addition, rifle bullets are often more aerodynamic, so they cut through material better. That’s why soft armor isn’t enough to stop them.
What’s Best for Defensive Handgun Use?
If you’re carrying a handgun for defense, you want ammo that’ll stop the threat without going too far. Hollow-point bullets are the top choice for most folks because they expand on impact, dump their energy into the target, and don’t overpenetrate. FMJ rounds are great for practice because they’re cheap and reliable, but they’re not ideal for stopping a threat.
When it comes to body armor, BulletSafe’s VP4 Level IIIA vest is built to handle the most common handgun threats, including FMJ rounds. And if you’re worried about rifle rounds, you can always pair it with hard armor plates for extra protection.
Conclusion
The idea that FMJ bullets can punch through any body armor just isn’t true. Rifle FMJ rounds are a serious threat, but most handgun FMJ rounds—even powerful ones like .44 Magnum—get stopped cold by Level IIIA body armor. Knowing what your gear can handle and choosing the right ammo is key to staying safe and prepared.
At BulletSafe, we’re all about making sure you get the protection you need without breaking the bank. Our Level IIIA armor has your back against the most common handgun threats, so you can feel confident when it counts.