Rob Curtis got the scoop on a new SIG Personal Defense Weapon. The SIG MCX, as Rob speculated it will be named, is the big brother to their recently launched SIG MPX pistol-caliber carbines. Internally all we know is that it uses a AR-15 style rotating bolt and a short-stroke piston. The upper will be compatible with AR-15 lower receivers. Externally we can see that it is integrally suppressed and does not have a buffer tube.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Michael Pham

    Is that… 7.62 x 39 in that strange banana mag?

    • Suburban

      I think that’s a pretty safe bet.

    • bbmg

      “The end-user can switch between 5.56 NATO, 7.62x39mm and 300 AAC.”

      • FourString

        Frickin’ sick. Will this be different from the SIG 516 because of the integral suppressor? Or will there be an unsuppressed version that simply has different ergonomics or perhaps an entirely reworked system compared to the SIG 516?

        • TCBA_Joe

          If it’s anything like the MPX, the operating system is completely different than the 516.

          The ergonomics and manual of arms appear to be the same as the AR, but with a different operating system and upper design.

          • FourString

            Cool. Yeah the upper definitely looks different. All in all it appears to be a more compelling design than the Sig 516

          • It’s hard to say at this point since this was top secret until last week.

        • FourString

          lol i would get downvoted for an honest question -.-

  • TCBA_Joe

    More info and pictures from Soldier Systems Blog

    Named “Halo”, and comes in quite a few different configurations.

    • JumpIf NotZero

      No…. That’s the pistol version. You can tell because of the small MP5-like magazine, and general reading comprehension and whatnot. MP(istol)X != MC(arbine)X

      Although I will give you that Sig appears to be sharing modular handguard design with this. And there is still a lot of photoshop on those MPX pics. So I wouldn’t expect anything to be on shelves very soon.

  • Michael

    How about a dedicated civilian Personal defence Weapon

    • JumpIf NotZero

      Personal Defiance Weapon more aptly

  • Yay! With more companies starting to offer AR-15 PDWs, it should be easier for people like me who actually want to assemble PDWs from parts to actually build the gun they want 🙂
    Very slightly.
    God, how I hate this general firearms shortage.

  • IXLR8

    That is an pretty big PDW. I am a Sig Fiend, and generally love and respect all of there designs. Unfortunately this is more of a Carbine, than a PDW.
    I want to own the first MPX on my block, which more closely mimics the the features of a PDW.
    The MCX will probably do very well for Sig, probably better than the 516 for sure. Suppressed ammo ballistics are equally dismal. I would rather have the heavier 9mm, over neutered 5.56 which gains all of it’s performance from velocity, which is missing in a subsonic round.

    • TCBA_Joe

      I’m not sure why it’s labeled as a PDW, other than the fact there’s a PDW version of it. It’s most definitely a carbine with an 11.5″ 5.56 bbl.

      However, they showed off a super short version (~7″? 300BLK?) of what I would guess is is the “PDW” variant. Pics on Soldier Systems.

    • Cymond

      I assume most people will use supersonic ammo most of the time. Why assume subsonic? If subsonic performance is really a big deal, then 300 Blk addresses that role very well, while still allowing full supersonic permance when needed.

  • Would be interesting to see whether SIG would sell just the upper with the sliding stock to allow users to mount it on their own AR lower? I could see that being a bigger market than selling entire rifles. Or is there something that would prevent just mounting this on your own AR lower?

  • Rob

    Despite ‘HALO’ being used on small placards in Sig’s booth, two of Sig’s employees said this firearm will not hit the market with that name. ‘HALO’ is Sig’s internal name for the project.


    You have great articles… I feel GAD coming on with this. Gun Acquisition Disorder. The SIG MPX is a cool kit gun but highly under-powered. But now with this MCX…wow. I just picked up a SIG 556R and I am in love it. Great rifle. Paired with my AMD-65. Heaven.