AWA reminded me that a couple of months ago on a Friday Feedback, reader It’s Just Boris asked this question:

Hm. How about an article looking at 5.7×28 out of handguns as a self defense round? Seems to be a blooming (mushrooming?) caliber these days.

I finally got around to answering it.

The short answer is that the 5.7 in its commercially available form is a novelty round that fails to adequately answer the question asked of it.  I say that as someone who has owned an FN Five-Seven for over a decade.

A brief history of the 5.7×28 is where we should start.

The 5.7×28 was developed in the early 90’s at the request of the miliary for a PDW.  A PDW or Personal Defense Weapon is a small arm that has power between a pistol and a rifle, for soldiers who don’t primarily use rifles but may need to in an emergency.  Perfect examples are artillery crews, tank crews, communications specialists, etc.

Traditionally, these soldiers were equipped with pistols.  At times, specialty pistols like the Artillery Luger and C96 Mauser that could be fitted with buttstocks (and sometimes in a full auto configuration) were issued to extend the range of these guns to provide more than short-range pistol defense.

After the development of the submachinegun, that weapon filled that role.  The M3 Grease Gun was issued to tank crews until the 1980s.

With the advent of body armor, the submachinegun became somewhat obsolete.  The idea of the PDW was a weapon that was the size and weight of a submachinegun but had the body armor penetrating capabilities of a rifle and a slightly extended range.

That required a new cartridge to be developed.  FN created the 5.7×28 and H&K created the 4.6×30.  Both took advantage of the weakness of soft armor and steel plates, that a high velocity, small diameter bullet would penetrate where a large diameter, slow bullet with more energy would not.

Both cartridges pushed very light, small-diameter bullets at velocities above 2,000 fps, which would defeat 90’s era military body armor.

The irony is that the PDW eventually became useless.  All the global powers that issue body armor, issue armor that can defeat the 5.7×28 with ceramic plates.  The military hates issuing multiple types of rounds (the Army hated supplying 30-06, 30 Carbine, and 45 ACP in WWII, and one reason to go to the 5.56 was a common platform of long gun simplified ammo logistics).  Weapon technology improved so that guns in rifle cartridges like the 5.56 could be shrunk down in size enough to make them effective as PDWs.  Why issue the M4 and P90 with different rounds and different magazines when you can issue a SIG Rattler that is the same size, and even out of a 5.5-inch barrel, the 5.56 has better performance than the 5.7×28?  The last holdout was the US Secret Service, who wanted a gun the size of the USI they used to issue, but could defeat body armor.  They ultimately came to the same decision as the military and switched to very short barrel AR pattern guns in 300 BLK, which has better knockdown and armor-defeating capabilities than the 5.7×28 (a 110 gr bullet 300 BLK from a 5.5 inch barrel is running 1700 fps, which is 700 ft-lbs of energy).

Back to the 5.7×28 and the two FN guns designed to shoot it, that would hit the commercial market.

The problem is that in the US it is illegal to sell armor-piercing handgun ammo.

So, to make the round commercially viable, FN partnered with Fiocchi to download the 5.7×28 to a lower velocity and use a heavier, polymer tip (Hornady V-max) bullet that made the round non-armor piercing.  It was neutered to make it legal.

There was, briefly, an American company that loaded several variants of the 5.7×28 to its original glory, and he got shut down by the ATF.

There are a few commercially available rounds.  A 40-grain FMJ at 1650 fps and 240 ft-lbs, a 40-grain polymer tip at 1750 fps and 270 ft-lbs, and a 40-grain Speer Gold Dot at 1800 fps and 290 ft-lbs.

Notice how all of them have less energy than a standard pressure 9×19 mm which is 115 grains at 1150 fps and 340 ft-lbs.

At low velocity, 224 caliber FMJ are not known to yaw, which is one major complaint about the 5.56 at extended distances.  The polymer tip bullets also, were designed to expand at much higher rifle velocities.  Their performance is reduced from pistol velocities.

The Gold Dot seems to be the best performer, with a bullet actually designed to perform out of a pistol-length barrel.  Vista product literature shows expansion in the approximately 0.35 inch range.  Which is the diameter of an un-expanded 9mm.

There are some YouTube videos that show the Gold Dot penetrating some forms of armor panels, but inconsistently.

Knowing the firearms industry the way I do, I suspect that the Gold Dot is not a regular armor piercer, because if it were, the ATF would take a giant shit on them and then they would open themselves up to lawsuits for selling cop-killer bullets.  My suspicion is that the armor panels being tested on are not the best quality armor.  I certainly wouldn’t start carrying a 5.7 loaded with Gold Dots in case of a bad guy wearing armor.  Any plates rated to stop rifles will stop this.  The only defeats I saw were on handgun-only rated panels.  Again, the irony is that plates have become so cheap and prolific that you are more likely to encounter a bad guy in rifle plates with plate carriers than you are in more expensive soft armor.

The one advantage that the 5.7 has is that the smaller diameter increases magazine capacity, but again, just barely.

The Five-seveN and Ruger 5.7 hold 20 rounds, and M&P 5.7 holds 22.  My SIG P320 holds 21 rounds of 9mm in a magazine that is only three-quarters of an inch longer, and my P365 holds 17 in a much more compact pistol.

My honest assessment is that the 5.7 is more of a novelty than a serious replacement for the 9mm in any sort of personal defense for concealed carry application.  The ballistic performance isn’t substantially better in any way.

If armor penetration were a concern, I’d rather have a 5.56 or 300 BLK pistol or SBR where I know my performance is more of a guarantee than a hit-or-miss YouTube test.

I have one that I haven’t shot in years.  I bought it when I was young and dumb and didn’t have kids and was making stupid money for a single guy.

Also, the ammo is more than $1 per round for a box of 50, so it’s an expensive gun to feed.

If you want one, this is America, you can go and buy one.  If I didn’t already have one I wouldn’t.

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By J. Kb

8 thoughts on “Answering a question from Friday Feedback – opining on the 5.7×28”
  1. Exactly the same information the guys in my neck of the woods have been saying. I never looked into the round and wasn’t sure I was hearing the truth. It’s good to know I’ve been hearing accurate info. Thanks J,Kb.

  2. Thanks much!

    One thing I noticed when handling the S&W pistol: the slide is very easy to rack compared to other pistols. That is a point in its favor for older shooters, perhaps.

  3. I have always wondered about the 5.7. I never had interest in one as your suggestion of an SBR in 5.56 I have one, 10.5 inch PSA upper on a Bushmaster lower. Handy AND has a bite. When the 5.7 came out I heard the “penetrating body armor “ brag and was kinda “meh”, it remains to be seen. your information shines a light on it. Good to know.

  4. I have a coworker who wants to carry one in a chest holster to “pierce the armored cage around reptilian hearts”. He bought the Ruger 5.7, didn’t like it, has ordered the PSA Rock, and ordered a mess of ammo from a company selling something called “Black Fang Obsidian Dragon” rounds

    So…..theres that at least?

  5. Interesting take but there are some caveats:
    -. the cartridge was developed in the 80s, not the 90s – that is important as the widespread use of ceramic armor began in the 90s
    – fun fact: the roots for the 4,6×30 go even further back – I think the 70s or even 60s
    – NATO standardized the 5.7×28 in 2021 and over 40 countries are using the 5.7 either for police or military applications, this is not a “novelty”
    – both rounds defeat even current military body armor, that is: soft armor and most helmets
    – hard armor protects only a small area of the body – saying the round is ineffective because it can’t defeat hard armor is like saying: “Oh no, the barbarian is wearing a chain mail bikini – our swords are useless against her!”
    – 5,56 and .300 BLK also cannot defeat hard armor
    – SBRs are LOUD and produce a very noticable muzzle flash – extremely short guns like the Rattler with a 5,5″ barrel even more so
    – 5,56 and .300 cartridges are considerably longer thus require longer, heavier actions which makes for shorter barrels and more reciprocating mass in similar seized and weighted package (the Rattler and P90 are roughly the same length and weight but the P90 has double the barrel length, the MP7 has a longer barrel than the Rattler but is roughly 2 pounds lighter – and both are more comfortable to shoot without the massive muzzle flash)
    – the 4,6 and 5,7 out of a MP7 or P90 are far more controllable than either the 5,56 or .300 out of a SBR
    – the concept was to issue the 5.7 instead of the 9mm, this would have not made any logistic complications
    – the 5,7 is far flatter shooting and faster than the 9mm – this is not as important for civilian self defense but an important factor for the intended role of the PDW in a military context

    You are right about how the round functions in a civilian context but as for the military context: the round does exactly what it was designed to do and does it very well and without any real alternative.
    The main reason these rounds got a bad rep is because the military is stupid: it’s not a round that is to be carried as a primary by a door kicker (the group of people that want SBRs) or, as the Germans do it, by an infantry group leader – who should carry a standard rifle as he is leading from the front.
    It was not designed for that role!

    Fun Fact #2: At least for the 4,6x30mm there are rounds that can and WILL defeat SK4 hard armour (similar to Level IV) at at least a 100m. I know because I tested these rounds and lost that bet against the chief engineer. (you are not the only one who was/is working in the industry).
    I don’t know if there are similar rounds for the 5,7 but given that it has about the same diameter as the 5,56 this seems unlikely – it’s the small diameter of the 4,6 coupled with a very heavy (ca. 4g, ~60gr !) projectile that achieves that performance.

    1. The 5,7×28 was not designed for the civilian user.
      As was the 4,6×30.
      But both are available to civilians and people are bying them. So… mission accomplished 😀

      (I can buy rifles for the 4,6×30 in Germany… there is not a task that this combination will perform well except separating a customer from his money.)

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