Is 5.7x28mm Just Overpriced .22 Magnum? [Part 1] By: Chris Baker

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Everybody loves to argue about 5.7x28mm. It’s been the subject of myths and wild speculation since its introduction in the early 90s. In this two-part series, we look into some of that history and put the 5.7’s ballistic capability to the test.

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Details are in the video below, or keep scrolling to read the full transcript.


Born out of a Cold War-Era NATO project, the 5.7x28mm cartridge eventually found its way into the hands of some of the world’s most elite military and law enforcement units. Along with its original host weapon, the FN P90, it’s been featured in dozens of movies, TV shows, and video games. It’s been a target of fear-mongering gun control enthusiasts. And shooting enthusiasts have debated the pros and cons of the cartridge for decades.

The popularity of 5.7 has swelled somewhat in the last couple of years, bringing that old debate back to the forefront. Is 5.7×28 any good for self-defense, or is it just a gimmick?

Hey everybody, I am Chris Baker from LuckyGunner.com and this is the first of a two-part series about that very topic.  Today, in part one, we’re going to explore the history of the cartridge, its effectiveness, and how it’s been received by military and law enforcement. In part 2, we will examine modern loadings of 5.7 and consider whether it’s a viable choice for the armed citizen.

5.7x28mm: The Beginning

Back in the late 80s, a request came from NATO for a new cartridge and a firearm that we now call a PDW or Personal Defense Weapon: a super-compact submachine gun for support personnel who are not expected to see combat. As kind of an after-thought, NATO also requested a handgun for this new cartridge.

Since it was supposed to replace 9mm pistols and submachine guns, the new cartridge was expected to have improved ballistics, including some armor-piercing capability. That could be the topic of another video by itself, but I am not going to dwell on the armor piercing issue today.  If you want to dive into that rabbit hole, there are plenty of other resources out there. For this discussion, I’m going to focus on unarmored opponents.

The FN P90 fired one-handed in full auto. From an FN promotional video

The NATO project ultimately fizzled out, but some of the proposed cartridges survived including 5.7x28mm from Belgian arms-maker FN. Their first 5.7 offering, the P90 submachine gun went on sale to military and law enforcement in 1990. Eight years later, they released the FiveSeven pistol, which we covered in detail in a recent video.

In the hands of FN’s marketing team, 5.7 transformed from a niche cartridge intended for non-combat personnel to a ballistic powerhouse ideal for entry teams and close quarters combat. While it hasn’t been adopted for general issue by any of the world’s larger militaries, 5.7 has been picked up by enough individual units and agencies to remain in production for over 30 years. When you consider that most new cartridges come and go within just a couple of years, 5.7 looks pretty successful by comparison.

From the very beginning, outrageous claims have been made about 5.7’s potential. At a ballistics symposium in 1989 (when the cartridge was still in development), a rep from FN supposedly claimed that it creates a wound cavity two times larger than .44 Magnum. Early advertising from FN proudly boasted performance “greatly superior to 9mm.”

Now that we’re a few decades in, 5.7 has been used long enough and in enough different types of armed encounters that we should be able to find out whether these claims are true. But first, let’s take a closer look at the cartridge itself.

5.7 By the Numbers

Despite its reputation, there’s nothing especially novel about 5.7x28mm. It’s basically just a .22 caliber bullet in a bottle-necked centerfire case. It looks kind of like a miniature 5.56.

Typical bullet weights range from 27 to 40 grains. With a 10-inch barrel like the P90, official loadings offered by FN reach velocities from 2000 to 2500 feet per second. With the pistol, that drops to 1600 to 2100 fps.

If you want to annoy a fan of 5.7, you can say it’s basically the same as .22 Magnum. That’s not totally fair, though. The two cartridges have comparable bullet weights and velocities, but only if you compare a 5.7 pistol to .22 Magnum out of a rifle-length barrel.

On the other hand, the 5.7 evangelists are also comfortable with exaggeration. It’s not uncommon to hear claims that it’s “basically 5.56 NATO out of a pistol or submachine gun.” That’s quite a stretch. They might share a common bullet diameter, but 5.56 has a lot more energy to work with.

Let’s take, for example, SS198LF. This is the non-armor piercing hollow point that FN is currently marketing to law enforcement. It’s got a 27-grain bullet that gets about 2400 feet per second out of the P90. A 10-inch AR-15 gets comparable velocity with a 62-grain bullet.

5.56 is often considered minimally acceptable as a rifle cartridge. It’s just not reasonable to expect rifle performance out of a cartridge like 5.7 when it has the same velocity and less than half the mass.

That doesn’t necessarily mean 5.7 is a bad round. It just means that we’re firmly in pistol ballistics territory. So the big question becomes whether 5.7 offers any clear advantages over other pistol cartridges, specifically 9x19mm.

The Temporary Cavity

The most common argument in favor of 5.7’s superiority is its armor piercing capability. But we’re setting that aside for now (And, for what it’s worth, LE and military also have access to armor piercing 9mm loads). But let’s look at what’s probably the next most common argument for 5.7: the temporary wound cavity.

I talked about the temporary cavity in detail a few months ago in our video on the basics of terminal ballistics, so you might want to check that out if you’re not familiar with the concept.

The gist of it is that when a bullet enters soft tissue, it creates a temporary cavity that can cause significant trauma if it’s large enough. However, most handgun cartridges lack the velocity to achieve this. Most tissue is elastic enough to absorb these smaller temporary cavities without serious damage. When they do cause damage, it’s often not enough to have an immediate effect on the target.

In ballistic gelatin, that damage is represented by tearing that radiates out from the bullet’s path, which we’ve exaggerated in these images so you can see it better. To create an effective temporary cavity, most bullets need to reach a velocity of at least 2000-2500 feet per second.

5.7 is capable of reaching this velocity, which is probably why people sometimes refer to it as a “mini rifle cartridge” or otherwise imply that it’s in a class above the typical pistol round.

But the bullet’s mass, as well as its shape and its material construction of are also important parts of the equation. For example, in the terminal ballistics video, we compared a .223 and a .308, both with Barnes TSX bullets. The .223 created a decent temporary cavity but the .308 was truly devastating.

Even though the two bullets had comparable velocity, the .308 had nearly three times the mass. It’s not just velocity that matters. The temp cavity comes from velocity plus mass plus a bullet design optimized for the cartridge.

5.7x28mm Ballistic Gel Testing

So what kind of temporary cavity do we get from 5.7? Well, here is that SS198 law enforcement load out of a 16-inch PS90. It looks pretty dramatic on the high speed camera. When we measure the damage left behind, we’ve got an area that’s 3.5 inches high and about 4 inches long. That’s not a whole lot better than what we get from a typical pistol round like this 9mm HST.

We also can’t ignore the shallow penetration. The bullet made it to just 8.5 inches. We fired a total of five rounds into this block of gel and the farthest any of them got was 9.8 inches. That is well short of the generally accepted minimum of 12 inches.

Somebody always asks why it’s 12 inches when the vital organs are clearly not 12 inches deep in the chest cavity. There are a lot of reasons that I won’t get into, but it might help to think about it like this. If I’m the bad guy and I turn this way, it’s about 12 inches from my arm to the middle of my chest.

We also tested SS198 with the FiveSeven pistol and the Keltec P50. The performance was not a whole lot different than with the PS90. Shallow penetration with an unimpressive temporary cavity. It does not expand or fragment – not that you’d want it to, because that would only make it penetrate less.

So let’s look at a different load. This is SS197SR, which is the load FN markets for civilian use. It’s got a 40-grain V-Max bullet, so it’s going to have a bit less velocity than the previous load. With the FiveSeven pistol, it only gets up to 1700 feet per second. And we don’t get much of a temporary cavity. But it does (just barely) penetrate to about 12 inches and all five rounds expanded nicely as well. So it’s not exactly outstanding performance for a handgun load, but you could also do a whole lot worse.

Unfortunately, when this round gets a little more velocity behind it, performance suffers. The longer barrels got it past the 2000 feet per second mark. Penetration dropped to about 10 inches on average.

Feedback from the Field

It’s not looking good for 5.7 so far. But gel testing isn’t everything. We still have 30 years of real-world use to consider.

I hate to bring it up, but someone always does: the clearest example of 5.7’s potential effectiveness was probably the 2009 shooting at the Fort Hood military base. 13 people were killed and 29 wounded, leading to calls to ban the cartridge and the FN FiveSeven pistol.

I’m sure if we were able to dig into the autopsy reports from that incident, we could learn some things about what 5.7 does, mechanically speaking. But ultimately, the question is not whether 5.7 is effective for assaulting (mostly) unsuspecting and unarmed victims. We want to know if it’s likely to quickly incapacitate a determined armed attacker.

Of the feedback I’ve been able to find from military and law enforcement who have multiple uses of force with 5.7, no one seems to be particularly happy with it. Initially, they all appreciate its ease of use, the low recoil, and the fun factor. The P90 is nice and compact and easy to maneuver in tight spaces. But opinions change quickly after they have to actually use it.

The late and highly respected Pat Rogers trained a number of personnel on issued P90s. He did not speak favorably of the cartridge. Multiple rounds were always needed to incapacitate, so they had to train to use full auto pretty much all the time. That required more training time and ammo than normal, which was a challenge because the ammo costs a lot more than other options.

A veteran SWAT officer at one department that issued the P90 had similar things to say, concluding with, “We have been using 30 P90s for five years now. There have been multiple bad guys shot with them. We will not be buying more 5.7mm systems”

An officer at a different department relayed a story where a suspect was shot 10-12 times with a P90 before telling the officers to “stop shooting me.” He surrendered, and ultimately survived that encounter.

The 5.7 of Today

Of course, we could find plenty of examples of failures to incapacitate from any cartridge on the planet. But in this case, I have actively been looking for a positive report about 5.7 from someone who has had to use it against human aggressors and so far, I have not found a single one (if you know of any, feel free to let me know).

That said, if most people are using 5.7 loads like the two we tested in gel, it’s no surprise that they’ve had less than stellar results. There are a lot of other loads out there, including some small-batch boutique loads that claim to take full advantage of what 5.7 can really do.

Also, as we’ve discussed many times here, law enforcement and military needs are not the same as those of the armed citizen.

So in part 2, we’ll dive deeper into the civilian context. We’ll look at some non-FN loads like Speer Gold Dot, the infamous T6B from Elite Ammunition, and a couple of others.

In the meantime, if you need ammo, you know where to get it. Get it from us with lightning-fast shipping at LuckyGunner.com.

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