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Word comes via SIG SAUER’s new(ish) Instagram account that the civilian production run of MPX pistols has begun. A couple of TTAG writers have had their hands on the pre-production versions of the gun, and our first impressions of the MPX were incredibly positive. Not only is the MPX an agile and accurate gun perfect for everything from plinking on the range to home defense, but it’s really cool looking to boot. And that’s a HUGE benefit in a world where everyone and their brother has an AR-15, as standing out on the range and looking cool seems to be half the battle these days . . .

In an environment where very few truly “new” firearms are being developed, the MPX is definitely a welcome addition. The general characteristics of the internal mechanisms may resemble previous SIG SAUER products (like their 516 and 716 rifles), but with a completely new magazine and new barrel system, the MPX is much more than “just an MP5 clone.”

The road to this point for SIG SAUER has been a little rocky. Our sources had originally predicted a launch “within weeks” back in the first quarter of the year, but as the months slipped by and nothing emerged from the factory, we started to get a little concerned. We hear that the reason for the delays was problems with the surface treatment on some of the internal parts, an issue that has since been resolved.

The slow but steady launch of the MPX might have annoyed those of us waiting with bated breath to shovel our money at SIG, but compared to the shove-it-out-no-matter-what approach we’ve seen from other companies (*cough* Remington *cough*) it’s definitely the better and more appreciated method. SIG has a reputation for quality control and getting things right the first time, and their approach to the MPX line has been no different.

There’s still no word about the fate of SIG SAUER’s lawsuit against the ATF over the mis-classification of their rifle version of this gun, so word has it that only pistol versions will be launching and feature the newly re-designed slimmer arm brace. As for a timeline, rumor has it that we’re about 30 days out from the gun being available for sale.

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      • With a RRA PDS or Faxton ARAK piston upper you can build an AR pistol without a fixed buffer tube, no tax stamp necessary. (one of these will probably be my next project!)

        • But it can’t fire with the buffer tube folded right? In my mind, that’s the majority of the cool factor of a foldable stock/buffer, just making it smaller isn’t that appealing.

        • Unfortunately, RRA half-assed the PDS design so it can’t fit on a standard AR15 lower. It also can’t handle full-auto use.

      • I didn’t require a tax stamp for mine either. The sig pistol brace does just fine for AR pistols too. I used the term “SBR” more as a descriptor of its capability rather than its legal designation under the NFA. They are functionally the same thing; the difference between an AR pistol with brace and an SBR is more semantics than actual function.
        With that being clarified, not quite sure what a sub gun offers over an SBR/AR pistol with arm brace beyond aforementioned controlability.

        • he mentioned it in the article. Its *not* an AR, and that means something to some people. Everyone has an AR in their catalog, and most people own one or more. Its even getting to the point where non-standard AR variations are becoming common, and this is something that is actually new.

    • From the wording in the article, it sounds like a vanity issue. Another point is that there hasn’t been a viable (in some opinions) pistol caliber carbine design since the mp5. This makes sense in the world of suppressed arms that the .223 is still loud suppressed compared to pistol calibers.

      Just my .02.

      • I’ll accept that. So the advantages to a sub gun over an SBR are:
        1) Enhanced controlability
        2) Less noise
        3) With that, I will add less muzzle flash

        I suppose everyone has their preferences. I counter with reasons why an SBR may be preferable:

        1) Increased lethality vs pistol calibers, even with a shorter barrel
        2) Increased effective range vs pistol calibers, even with a shorter barrel.
        3) Commonly available parts and magazines
        4) The ability to simply switch uppers on an existing AR (If stamped as an NFA SBR), as opposed to a proprietary stand alone system

        All depends on a person’s preferences, I suppose. Me personally, the “better suppressed” argument loses out VS increased utility and lethality.

        • Agree with most of your points, however if your mission spec calls for you to be quiet, then the ability to usefully suppress the gun trumps many of the other points. 5.56 simply cannot be effectively suppressed. That all said, this makes the case for 300 BLK. A .30 round that can be run supersonic or subsonic with nothing but a magazine change.

        • Do you, or anyone else know how much velocity the 556 loses in a pistol length barrel? For states in which it is illegal to carry a loaded long gun in the car, an AR pistol with a sig brace might make a pretty decent trunk gun.

        • Old Ben turning in grave,

          According to Quickload with a 55gr FMJ loaded to 55k PSI with Alliant AR Comp:

          20″- 3235 fps
          16″- 3072 fps
          12″- 2833 fps
          10″- 2664 fps
          8″- 2437 fps
          7″- 2290 fps

    • May be true, but most of my guns weren’t really purchased because of total usefulness I mean why do I really need the four 12 gauges I have? It’s cool to something new, I’m personally sick and tired of 1911s and AR 15s

    • Well SWAT prefer 9mm MP5 for room clearing in Apartment buildings and office buildings since 9mm hollow point has less chance of over penetration of thin walls.

      • It’s a myth. 9mm has higher chance of penetration than 5.56 for most loads (5.56 fragments, thereby shedding energy very fast). But both will penetrate several walls easily.

        • Ah, this again. The FBI tested 9mm NATO loads (147 gr @1200), which are known fore their extreme penetration. The M16’s, on the other hand, when they did fragment, they penetrated far less. Now that appropriately engineered HP’s are available for both, and the FBI can use them, there are perks to each. Pistol rounds provide greater area for dispersion of their minimal energy, and rifle rounds violently expand and upset, dumping energy explosively, and having similar performance thereafter as an expanded pistol round. both will penetrate multiple walls, and both will go through a similar number of walls. PC’s would be better with regard to noise and possibly recoil, rifle rounds for maximum tissue damage.

    • A better question would be what a .223 PISTOL can’t do.

      Then its an apples to apples comparison.

      And I’ll answer it for you. Pistol caliber guns are better than .223 for some people because its:
      1) cheaper to reload
      2) easier to reload
      3) cheaper to buy
      4) better to use if you want to run a silencer
      5) less noisy without a silencer
      6) able to be used at ranges that don’t allow centerfire rifle ammo.

      Thats basically it. No practical reason. This gun is all about fun.

    • Try shooting that 5.56 sbr (I mean, pistol) without hearing protection.

      For a home defense option, pistol caliber like the mpx is far more forgiving than the 5.56 that would obliterate your hearing.

    • Also… My AR’s would require alot of work to shoot .40 in a less than optimal platform. This gun with a 6 inch barrel and my .45 octane attached would be a sweet set up

    • A 9mm is designed for application in pistol barrels. As such it will use most of its energy to propel the projectile. To achieve the same efficiency with 223 rounds, one will have to reload and use a faster burning powder, otherwise much of it just goes into the “bang” and the “flash”. Then it becomes complicated because you will also need to consider rate of twist and weight.

      Now, personally, I prefer a 9mm also because it’s widely available, I pay 0.36 for JHP, and 0.24 FMJs. With that I can shoot a lot more.

      If you are concerned about over-penetration with Home Defense (I read a few comments of that nature) get a Ruger 10/22. It will do the job with good accuracy. It’s not an absurd proposition.

  1. Looking cool is not half the battle these days….its been Rule #1 from day 1.

    Rule #1: Look cool.
    Rule #2: Know where you are.
    Rule #3: Don’t be an idiot.

  2. SIG has a reputation of releasing things right the first time? I beg to differ. The first 238s had a “mandatory safety upgrade”, the 516s had a problem with the op rod the 556R was a disaster that took almost a year to fix, and the 290 was so bad they redesigned it to become the 290RS. Hopefully they learned from these mistakes and actually stopped rushing things out the door.

    • The 290 turning into the RS turned an easy to handle gun that Ralph shot to 75 yards (and i shot well inside of 8 yards as designed) into a trigger finger calisthenics course that resists being aimed with any consistency that is gritty and breaks so far back it hurts your phallanges to actuate.

      Some stuff does not need fixing.

  3. I ended up with a Sig lower for my “SBR” / support-braced “pistol”. While I really like the package as a whole, I’m less than thrilled with the Sig receiver.

    Issues I’ve encountered:

    * Can’t install the Magpul BAD lever, which I’ve trained myself into using with the rest of my “family” of ARs.

    * I do like that it has QR attachments milled into the receiver, HOWEVER, the most desirable place to put it interferes at times with a clean “safe” of the gun as it comes off my shoulder. That wasn’t a bright move by the enginerds at Sig.

    * The factory Sig trigger didn’t wow me at all for a $1200+ base gun. If fact, I ripped it outta there and put in a RRA 2-stage. It wasn’t horrendous like a DPMS factory trigger, but it wasn’t nearly as light nor as clean as I’d have liked – or expected from a premium (priced) gun.

    Sig rifles – at least the couple I’ve shot aren’t bad guns, it’s just that they aren’t a good value.



  4. I don’t see how this is a huge benefit over the AR-15 when this is just a glorified 9mm AR-15. I was excited for it until I learned that the charging handle is still right in your face, the bolt catch/release is in the same position and the trigger parts are the same. If I wanted a 9mm AR I would just save a ton of money and get a 9mm AR.

    Also Sig does NOT have a reputation for QC and getting things right the first time with their rifles. In fact it is the complete opposite. They are known for messing up their first attempts at just about every rifle they try. The 556xi having the issues with the bad gas tubes is a perfect example.

    With anything Sig makes that isn’t a variant of their tried and true handguns, you are better off waiting for the revised version with the fixes they will need.

    • the MPX is a lot closer in function to an HK MP7 than a blowback 9mm AR, so keep that in mind when factoring cost.

  5. The thing to keep in mind is that the MPX can do other calibers too. They’ll have it in .40 and .357 sig. I’m waiting for the latter. I have zero interest in a 9mm subgun. That’s what my Uzi is for.

    • Now a pistol caliber in .357 SIG would be something!

      (it would also be nice to have an option for 7.62×25, just for the sake of cheaper ammo)

  6. Beretta CX4 Storm 9mm carbine. I love mine. Great handling and ergonomics, accurate, fun as heck, and completely reliable.

  7. 2 months later and I’m still waiting for my 556XI to get back from the Factory after it got megajammed. Sigh. Worst decision ever.

  8. Why do people seem to be against having options? Believe it or not your gun doesn’t need to more tactical. Every gun doesn’t need to be a Ar 15. I’m personally not going to buy a MCX but for some it may be perfect, and fun, and maybe better for niche purposes. For example firing a AR15 pistol even with a SIG brace can have nasty muzzle flash and is loud as hell. I would love to see semi auto MP5s and UMPs be common and affordable.

  9. Like other above have said… 5.56 is not very advantageous in an SBR. If they offered this in 300BLK – which is specifically designed for SBR, it would be awe-some, hands-down, kick ass.

  10. I’m looking at this for a fun high-volume plinker, ease of reloading 9mm with hard cast bullets, less powder, much simpler brass prep and much better brass life than 5.56.


  11. A “pistol”. I sure hope they do come up with some way of mounting their “arm brace” to it…

  12. When you need reasons beyond “it’s neat and I like it” to buy a gun, this has stopped being an America in which I want to live. Utility? What are we, communists?

  13. In the video from the review, did anyone else notice the magazine rocking back and forth as the weapon cycled?

    • I could re-release a top break revolver and still…not be CA compliant.

      The fact that handgun safety is not the issue is what kills me. Hi Point firearms are not safe all the time. Cheaper revolvers suffer from issues that prevent cylinder lockup after a hundred lead rounds, where lead builds up to cause that i have no clue but…it isn’t about actual safety of the handgun for the masses. That was off topic but it irks me.

  14. “Looking cool seems to be half the battle these days . . .”

    If you’re even thinking about trying to look cool, you’re so far from ever being cool as to go ahead and declare that battle a complete rout before it’s ever even been fought. If you insist on making up rules, then this is the one rule to rule them all: the first (and only ) rule about being cool, is don’t talk (or think) about looking cool.

  15. Ordered the MPX-C and the standard pistol version 3 years ago and I’m hoping Sig is producing the standard pistol version without the arm brace because that’s what was available to preorder at the time. Ashame the C rifle is in jeopardy due to the ATF being stupid. The pistol version is my preferred choice. Sig red dot and can’t wait to SBR it or add a Sig Arm brace myself.

  16. All I got to say about this rifle sorry “pistol” is with it cambered in 7.62x25mm for the win.
    Have your cake and eat it too.

  17. Just called Cabelas bc their website listed the MPX now.

    I was told that they did have a few of them in but they got recalled by Sig already. The guy seemed to think they wouldn’t get any back in until the end of Jan.

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