Modern Personal Defense Weapon Calibers 001: Introduction, and the 5.7x28mm FN

Four PDW calibers: .22 WMR (Kel-Tec CMR-30 and PMR-30 SMG), .22 SCAMP (Colt SCAMP), 5.7x28mm FN (FN P90), and 4.6x30mm HK (HK MP7).

At this point, we’ve talked about 25 different intermediate and full power calibers as part of a series comparing different types of modern small arms ammunition. However, one subject not yet thoroughly covered is rounds for personal defense weapons (PDWs). These weapons are designed to be smaller and less obtrusive than full size rifles, while being more capable than pistols or submachine guns, particularly with respect to armor penetration.

Technically, we’ve already covered five PDW calibers as part of the previous series; two of which were designed from the outset for the role. Those five were the 5.56x45mm NATO, 5.45x39mm Soviet, and 6.8x43mm SPC, three rounds designed as assault rifle rounds but commonly put into service with short-barreled carbines functioning as PDWs, and the .300 AAC Blackout and 6x35mm KAC/TSWG, which were designed from the outset for short-barreled PDWs.

However, all of those rounds can function as either PDW ammunition or assault rifle ammunition, and this series will focus instead on rounds that are too low performance to be considered assault rifle ammunition. In many cases, traditional pistol calibers like 9x19mm can be considered PDW rounds as well, and those may be covered later.

The first round we’ll be talking about is the Belgian 5.7x28mm FN, a .22 caliber high velocity round designed originally for the P90 submachine gun. Later, the projectile was shortened to fit within the grip of a pistol, which became the Five-seveN handgun.

Below, we compare two loads of the 5.7x28mm to the old 9x19mm M882 standard. Note that I have omitted the wind drift chart, as the differences in wind drift between calibers of this type at ranges 300 m and below really won’t matter (even the very different 9x19mm and 5.7x28mm have almost identical wind drift characteristics at 300 m):

(NOTE: There is an error in the graphs below. The 40gr V-Max of the SS197SR is listed as having an 0.084 G7 BC; the actual number is 0.100 G7. The data in these graphs is correct, it’s just the label that is wrong.)

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You can see how the 9x19mm has a substantial energy retention advantage due to most of its flight being in the lower-drag subsonic flight regime. 5.7x28mm, on the other hand, sheds velocity very quickly, even though its bullet is much better shaped for supersonic flight; by 300 m the SS190 has just over 100 J of energy left, barely enough to make a lethal wound. This drag problem is one of the most significant obstacles facing these pistol-sized small-caliber, high-velocity rounds.


Different loadings of 5.7x28mm: The two on the left are SS190 Armor Piercing (one with black tip, one without), in the middle is the L191 AP-Tracer, and on the right is SS197 Sporting Round with a blue-tipped V-Max bullet.


Besides armor penetration, perhaps the biggest advantage of the 5.7x28mm FN is the low recoil. We can see what a dramatic advantage this caliber has in two screenshots from’s recoil calculator, where it is compared to the 9x19mm M882 again:


A little more than a quarter of the recoil energy ain’t bad at all, that’s for sure.

Lastly, the 5.7x28mm and other small calibers of this type give a substantial advantage in the ammunition’s weight. While 9mm M882 weighs 12.6 grams (more than 5.56mm!), 5.7x28mm clocks in at a very modest 6.5 grams per shot.

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • PK

    Good overview. I look forward to a comparison between the .22 SCAMP, 5.7x28mm, and 4.6x30mm not only as far as external ballistics, but in terms of recoil energy calculated with their platform weight.

    The only one of those three I know well is the 5.7x28mm, of course, so using that as a baseline (or using 9x19mm for those who are unfamiliar with use of the relatively uncommon 5.7mm) will give a great bit of insight as to actual efficacy.

    I know I’ve said it before, but when you have covered the cartridges you set out to write about, I do hope you compile this all into a textbook. I can’t be alone in wanting a hard copy in my library.

    • Trey Heldmann

      You certainly are not, this series is awesome and I would love a hard copy of it. Saying I am no expert in ballistics is an exaggeration, my knowledge of this subject is extremely basic, I have learned so much and am extremely grateful for Nathaniel for putting it together.

    • Jared Vynn

      22tcm is another one that should be covered, it performs a lot like .22 scamp would.

      • iksnilol

        Only difference is that you can actually get .22 TCM 😛

      • iksnilol

        Only difference is that you can actually get .22 TCM 😛

      • noob

        does 22tcm perform differently than 22tcm9r? that was another round that, like the 5.7 was shortened to fit into the pistol grip (of smaller pistols).

        notably the projectile shape is much less pointed. does BC become a big factor at range?

        also I’m surprised that the 5.7 has not been adopted by more firearms. Had it been adopted as the official NATO PDW round I’m sure you’d be seeing 1911s chambered in it by now.

        • The 9R has an even worse ballistic coefficient.

          I haven’t done the charts yet, but I suspect the .22 TCM is going to end up inferior to the 5.7x28mm at anything beyond handgun distances, because it’s going to bleed velocity too quickly due to its stubby bullets. That’s fine since it’s just designed as a high velocity handgun caliber, but that becomes a problem when you start trying to stuff it in a PDW.

          • ozzallos .

            They have a bolt action rifle made for it. 2800fps seems to be the going velocity out of a 22in barrel. There’s even a hog hunt video floating around somewhere, so it might surprise you.

          • Velocity is one thing, drag is another. Those bullets won’t stay fast for long.

          • ozzallos .

            Didn’t seem to matter in your review of the round paired with the rifle circa Dec 18th, 2015. And I quote, “…putting up consistent .5″ and under groups at 50 yards. Extrapolated to 100 yards, the rifle is a MOA shooter.”

            And look, there’s the hog video in said review. Neat.

          • Jared Vynn

            You should compare the loads for both rounds using 35 gr VMAX, also 22tcm would probably be better in a machine pistol or sub machine like the mp5 than a pdw like the p90. If you were to use 22tcm for a PDW you would be better off increasing the OAL to let you use longer bullets; you lose out on compatibility with handgun, but you get the greater velocity retainment over distance desired.

  • Paul O.

    The 5.7 fulfills its role. It penetrates soft body armor (ss190) and is effective out to 300 meters all in a package that is more compact than SBR’d carbines. One question is what’s it good for in the civilian world? Mostly, it’s a fun round with low recoil. The ss197 is also an adequate varmit round.

    • Younggun21

      In the civilian world? Unfortunately not much. It would be a great training round with lower recoil than full blown rifle cartridges, but the cost is almost equal to most surplus rifle rounds. It would be a great varmint round, but again there are more cost effective alternatives such as .17hmr, 22lr, 22mag, .223 etc. It would be a great defensive carbine for close encounters in the home but prohibitive legislation makes acquiring an SBR an arduous process to begin with. Tons of people would love to use it as a home defense weapon with an SBR and suppressor affixed (myself included) but not all of us have pockets as deep as uncle sam. If you want to do an SBR it is more cost effective to just do an AR platform and if you are going to do that you might as well stick with 5.56 or go to .300 blk for the energy benefits and reduction of parts cost.

      • valorius

        Nah, 5.7mm ammo is no more expensive than .45acp ammo, unless you want to go with Elite ammo, which is, sadly, quite pricey.

    • nova3930

      That’s my assessment. I put together an AR-57 SBR just for grins and it’s a ridiculous amount of fun. 50 rounds between reloads with basically no recoil but a lot of blast.

    • gordon

      I am not terribly confident in it’s terminal effectiveness either, but…. I have a 6″ pistol and use my own loads. It penetrates a IIIa panel and then consistently tumbles twice as consistently makes it to 14 to 15″. The tumbling blooms are 1.5 to 2″ wide and a bit two dimensional but occur fairly far along it’s path (6″ and 11″). I have no idea what the chance a civilian will face a soft armored attacker is, but suspect it is increasing.

      • valorius

        WWI and WWII proved that even .32acp’s can be effective in combat. Compared to a .32acp a 5.7mm is a death ray.

        I never worried at all about the terminal performance of Elite S4M ammo in my Five Seven pistol.

        • gordon

          I just switched from carrying T6B because I can more afford to practice with my own loads and since my loads are 45gr they also penetrate straighter. I like the large wound channel blooms of the lighter stuff but I am happy to trade it for smaller blooms further into the target.

    • iksnilol

      I think it is pretty good for civilian purposes. I mean, a P90 is small enough to fit under a jacket (let alone a coat), has 50 rounds, doesn’t snag and can be used out to 300 meters (which is like the practical limit for most folks.

      And considering the weight of the ammo, a loaded P90 with a couple of spare mags isn’t really cumbersome.

      Basically a good “Civilian Defense” carbine for your average joe. Shame the cartridge isn’t more common.

      • AC97

        And plus, it is actually possible to get ammo that goes through armor out of a Five-Seven (a P90 can go through armor with a wider variety of ammo, due to the longer barrel), like T6B and S4M (the former can go through three IIIA vests, while the latter can go through one).

        If it weren’t for the fact that the Five-Seven pistol is so godawfully expensive, and the fact that you have to convert the PS90 into an SBR, I wouldn’t mind having one of the two.

        Also, screw the guys that DDoS’d Discus, because it was frustrating typing this on a phone.

        • noob

          hmm. is there any other pistol that can take magazines long enough to chamber the fiveseven? 10mm auto is 32mm OAL. I think 5.7mm is 40mm OAL?

        • valorius

          I’ve personally shot Elite S4M from the Five Seven pistol through several IIIA vests. Even the best IIIA’s can’t handle that round.

    • Another thing to keep in mind is that the 5.7×28 has much less blast out of the PS90 then 5.56 has out of an AR-15. It’s a roughly 6gr powder charge vs 24gr powder charge for 5.56.

      Indoors without ear protection, that could be pretty helpful.

    • valorius

      Elite S4M and Elite T6 both cut through a IIIA vest like a knife through hot butter.

      I think the Five Seven would be a great patrol or armed guard weapon, for those that can comfortably handle it’s grip size.

    • ozzallos .

      I’m just going to say this… Have you seen the body armor penetration? Yes, it does, but the results on actual medium are far from impressive, let alone reassuring if you’re carrying it for that contingency. I know it’s not a popular thing to say, but short of full-auto spam, it’s amazingly meh.

  • TechnoTriticale

    Was .30 Carbine covered in the Intermediate series? If not, perhaps it belongs in this new series.

    • ostiariusalpha

      I’ve claimed that .30 Carbine belongs in the intermediate category before, though really, it’s kind of in that fuzzy, liminal area between the kind of magnums you’d typically see chambered in revolvers and what are commonly understood to be intermediate cartridges. The 6x35mm KAC is in the same boat, and has much of the same design philosophy behind it, but its power margin puts it closer to the intermediate camp than the old .30. Perhaps if it had been chambered in other successful firearms than the M1C, it could have had different bullet designs and more powerful loads developed for it; which would have more clearly differentiated it from the more potent pistol rounds.

      • Yep, and there’s also a problem with categorizing intermediate calibers vs. PDW calibers… It’s more of a spectrum than a hard line!

        • noob

          🙂 maybe we need a “periodic table of calibers”?

          we might be able to see a gap where there is a “missing element”

          • ostiariusalpha

            Such a graph might get a bit complicated, since metallic cartridges are defined by more factors than the periodic table’s arrangement of periods and groups; though you could make an argument that the primary features of a cartridge consist of its case head diameter, general volume, and projectile caliber. Unfortunately, that would gloss over some rather important properties that distinguish case designs from each other: operating pressure, for example, or case length, rim diameter, body taper, shoulder angle, and neck length. Two very important, and interrelated, elements are the cartridge’s overall length (COL) and action length, with the action length putting a constraint on the maximum dimensions that the overall length can extend to. This is actually a rather ambiguous area since action lengths are pretty soft categories themselves, and can therefore leave a lot of wiggle room about where the max COL should be.

          • noob

            I agree, it sounds like the real multidimensional table will have to be something like a manifold, and be analysed with something that shows where the gaps are, not the clusters.

            My usual go-to (principle component analysis) is for showing clusters only, so I guess we’ll need a mathematician.

          • ostiariusalpha

            Intuitive clusters, such as “cartridge families,” are pretty easy to find based on shared case head & rim diameters, since those are points of relative stability, combined with common COLs. From those you get the broader sense of a family of cartridges, with closer relationships formed by having more similar body tapers. For instance, the Mauser bolt face diameter forms a kind of clade, and from that class comes an order of cartridges defined by the short action firearms that are chambered for them, with the .308 family as a subset within the Mauser short action cartridges; the 7mm-08 and .358 Win being examples of the .308 family.

          • The Brigadier

            Don’t forget the powders and the primers as well. Those are two other factors that further muddy the waters. You also have a very long cartridge like the thirty-thirty varmint round that is inferior to the much shorter .30 carbine round. So even overall length is not a valid indicator in some cases. Perhaps you can have an oddball category for both rifle and handgun cartridges. You definitely have your work cut out for you ost.

          • ostiariusalpha

            I kind of just merged the powder and primer under operating pressure, since that is their primary effect. 5.56 and .223 are nearly physically identical, but the differences in powder and primer create separate operating pressures that make it important not to mix them up.

        • The Brigadier

          You are both right. I was sorry they didn’t make the case longer and lengthen the bullet to have a boat tail for accuracy and a Spitzer point for better flight. I am talking with some others and we are going to open an armory in West Texas. Fixing the M1 Carbine will be one of our main goals. We think we can do it with the same actions and the design of the bolt. The barrel might have to be lengthened a couple of inches also. It will definitely be more than just a magnum pistol round as it is lumped together with now.

      • TechnoTriticale

        re: …it’s kind of in that fuzzy, liminal area between the type of magnums
        you’d typically see chambered in revolvers and what are commonly
        understood to be intermediate cartridges.

        In a lot of web chatter over the years, people often sort of position it as a rimless .32-20 +P (rifle loading), although rimless .327 Federal Magnum might be closer.

      • BigFED

        Look at the 5.7MMJ. It is a round that Melvin Johnson created for the Carbine. It’s performance was far better than expected. It became popular south of the border because it was NOT a “military” round/caliber that most governments banned from common folks. It was NOT a round one wanted to be on the receiving end of (applies to almost ANY round for that matter)>

    • The Brigadier

      Yes, that round inflicted more casualties on America’s enemies than any other rifle we used and that includes Garands, M14s, M16s and M4s. It is an effective carbine for assaults and its light and the ammo is light to carry also. It makes a good PDW for the same reasons. The military rear sight has a 400 yard setting for it, and I saw kills made at the distance, but not that many. At 300 yards its an as$ kicker and you could do much worse than carry the “War Baby” into combat. I am happy that two companies are making this rifle again. I hope others start making it as well. That is another weapon I am going to buy soon.

  • Kivaari

    The drop chart does represent 9mm quite well.When using a Mini-Uzi at 100 yds. I could fire tracer rounds that showed the pretty flat path until about 90 yards, when it takes a nose dive. Stnadard bsll ammo would perform like the tracers. Fiocchi “combat” had a distinctly higher velocity and over came that 90 yard nose dive. I’d take that Mini-Uzi over the P90.

    • valorius

      Not me. Mini Uzi- ZERO ability to penetrate body armor, and more recoil than 5.7mm, with about half the mag capacity of a P90.

      Not even close.

      • Kivaari

        I just love the size. 14.75 inches when folded. 30 rounds, easy to hit with at 100 yds. Limited armor penetration is true. I used mine in civilian settings when body armor on the bad guys was minimal. Most of the time I was issued an MP5 and I prefer it over most small guns. If we go to SBRs, I’d take an M4, and have one.

  • marathag

    and for an oldie, .22 Spitfire, based off the .30 Carbine
    40 grains with 3000fps

    and the 22 TCM, based off the .223
    40 grains with 2800 fps

  • valorius

    Elite ammunition 5.7mm ammo REALLY makes this caliber shine.

    My Five SeveN pistol with Elite S4M ammo defeated every type of IIIA vest i tested it on. Including a US Armor vest that stopped several rounds that other IIIA’s wouldn’t.

    FN factory ammo is quite weak in comparison, though still effective for self defense IMO.

  • Michael Mabey

    One no one has brought up yet is 6.5×25mm CBJ

    • BigFED

      Not a readily available round! In fact, only heard about it in this article and I have been in business over 50 years!

  • Tassiebush

    This makes me ponder the idea of the .221fireball for a similar pdw role. Might not fit in a grip based mag well and no idea if feed would be an issue but the ballistics to barrel length would be a decent match.

    • The Brigadier

      Availability of ammo in that caliber is practically zero and after the SHTF it will be zero.

      • Tassiebush

        To be honest I doubt there’d be much scope for scrounging or resupply of virtually any round at all but all the same availability is a big factor for any choice of chambering. Without thinking about shtf contexts just in our contemporary context ammo availability is an issue anyway. I’d imagine it might improve if it were adopted across a few more platforms. It’s performance to weight ratio would leave a lot of pdw rounds for dead. Personally I just want to see it take off more in micro action length Bolt action hunting carbines.

  • Cmex

    So 5.7 only wins really in low recoil, because there are AP 9×19 loads. It loses in EVERYTHING ELSE. What a useless round!

    • BigFED

      Wrong on concept! Rounds per pound on any BUG out kit by a factor of over 2 (almost 3) to one, i.e. for every round of 9m/m, one can load out two/three rounds of 5.7×28!

      • Mazryonh

        Stopping-power-per-round is a thing, otherwise we wouldn’t be hearing about all these reports of failures-to-stop regarding most PDW rounds. Rounds-per-pound doesn’t help (except maybe for suppressive fire) if you need more rounds to hit to achieve the same effect as a somewhat heavier round would have.

        • BigFED

          Depends on situation! For self defense and unlimited availability, I could agree, but in THIS instance we are talking about long term survival where rounds count! Stopping power takes second place to having ammo! I could carry one round of the ammo with best stopping power or many rounds of what is in fifth place.

          In military thinking, it is better to wound many than to kill one (assuming one is facing benevolent enemy)! Wounded are usually out of the fight. And being able to inflict a second wound if required is better…

          “Stopping Power” is a mythical element that is never around when it counts! What works in one instance almost always never works in the next instance since the SAME, EXACT conditions NEVER exists in the real world! Wound path, material, bones, etc, etc.

          • Mazryonh

            I doubt most people could humanely drop a grown black bear with a Five-seveN handgun, whereas you have a much better chance of doing so with a Glock 20 loaded with full-power ammo. A Glock 20 also has a much better chance of piercing a car windshield or other light cover than a 5.7x28mm handgun as well. Ammo weight can’t trump everything.

            Yes, number of rounds count, but since we can’t all be expert shooters under all circumstances, rounds that make each individual hit count more are also useful. If a 5.7x28mm round fails to yaw once inside tissue you’ve destroyed less tissue than a 9x19m FMJ round would. 10mm Auto by contrast is much more consistent, has access to good hollowpoint ammunition, and also has excellent heavy subsonic bullets in case you need minimum sound when using a sound suppressor.

  • cwolf

    Don’t forget the Gwynn 556 arm pistol. Easy to shoot. But muzzle blast was ferocious.

  • BigFED

    I find it “interesting” that one factor NOT being addressed n this article is AVAILABILITY of the ammo! Most of these other rounds are NOT readily available across the counter. Good luck with finding ammo after an “event”! 9m/m will almost be universally available! Try looking for that 6.5 x25 CBJ and other such rounds! Even the .221 Fireball has limited availability! While the 5.7×28 FN may not be as widespread as the 9m/m, it is sure as hell will be easier to find than almost ANY of those other rounds! And don’t try to BS it with the old “I will reload…” Good luck on finding components…

    • The Brigadier

      I agree. I saw an article a year ago about which ammo will be readily available for barter or picking up on the battlefield after the SHTF. It was basically 5.56/223 and 9mm for the two primary carbine and pistol rounds, followed by .308, .45ACP and .357 magnum. If you buy weapons in any or all of these calibers, you will be equipped to battle with raiders all day long. I now have a new m4 and a CZ in 9mm to go along with my 4 .357s and a lone .45. I am looking at getting a new .308, but I am saving up for a SCAR and a longer bull barrel for it. The shorter barrels for the 17s are too slow for that powerful round.

  • The Brigadier

    Does anyone know if any company still makes the original longer cased ammo for the P90? I got to shoot one of the original bullpups in New Mexico seventeen years ago, and it was the most amazing smg I ever fired. At 50 yds every bullet went into the same hole. It looked like I was firing a water stream, and this little tiger was simply amazingly accurate on full auto. We also got to shoot fully automatic MP5s as well. On single shot very accurate, but it sprayed on full auto and the groupings averaged an eight inch diameter at 50 yds. I would like very much to own an original P90 if I can get a supply of the original longer cased ammo that was made for it. The one sized fits all mentality of the French and the Belgians is depressing. They shortened the case so they could have the same caliber for the P90 and their pistols. I assume it was to save money, but they ruined the bullpup with that new anemic round.

    • Mazryonh

      Were you able to see just how much longer the original P90 ammunition was compared to the modern version?

  • Jackson Andrew Lewis

    and 5.7 could be come common if the germans would just tel HK to suck it up that the 46 is worse than the 5.7…..

  • William Elliott

    I’d like to see the new 7.5 round from BRNO compared in the PDW camp. Given the characteristics, it might be close to that happy medium for a PDW round [2000 fps out of a 6″ barrel with a relatively streamlined 100 grain projectile]
    Assuming of course you can get some for testing or at least get the data.
    Keep up the great work.