Sig Sauer MPX 9mm sub-machine gun review

While 9mm SMGs aren’t as tactically relevant as they used to be, there is still a market and a place for them. I’m a huge fan of the Sig MPX, and now that they’re offering it in a carbine version makes me genuinely happy. 9mm rifles/subguns are awesome fun, and while they may not be as practical as a rifle, you can do a lot worse for a defensive firearm.


  1. It’s too bad that SIG really dropped the ball on this gun.

    – $70 mags
    – $300 stocks
    – The gun was supposed to originally come with an adjustable gas system, but they scrapped it
    – Suppressed, the MPX is extremely gassy. It’s identical to a 9mm AR, which if anyone has ever compared to an MP5 is night and day different.
    – The action is a tiny version of the MCX which unfortunately hasn’t been as reliable as even a blowback firearm and definitely not as much as the delayed blowback. They tried to improve upon the roller lock system and failed, which is really unfortunate.

    They did get the styling right. But at MP5 costs for everything, it’s just not worth it imo.

  2. I really want a ppc/sub gun especially in 9mm, but every time I get close to purchasing one I talk myself out of it. My reasoning is they are just pistols with longer barrels. BUT they are so cool!

  3. The gun looks cool, but the price point is absurd. How is this gun significantly better than the CZ Scorpion that can be SBR’ed or the newly introduced Scorpion carbine? The CZ is much cheaper and reviews are very faborable and positive as to function and reliability.

    1. It’s not better than the CZ. That’s the issue for SIG.

      They wanted a successor the MP5, and when they started working on it, they would have been selling like crazy. But now… The CZ is cheaper and imo probably more reliable long term, and absolutely suppresses better.

      So now they finally release the gun, have a crap launch, immediately update to a Gen2, charge just as much for their parts as HK parts. And have the CZ, the Vector in 9mm, MP5 clones in every direction you look, Uzi clones, the Uzi Pro, Tavor 9mm kit, a TON of AR 9mms that take Glock mags, etc. It’s just a totally different market now.

      IMO it’s the action they screwed up the worst on. There is just no reason for the MPX to have a complex action that ends up working just as poorly when suppressed as blowback AR.

  4. Over my lifetime I’ve sampled my fair share of 9mm class SMG’s from the Bergmann MP18 to the HK MP5. IMO the best of the bunch is the Carl Gustav M45 (aka Swedish-K). The M45 is heavy and has a slow cyclic rate, very accurate and just chugs along without any stoppages–plus it looks cool.

  5. The MPX looks like a cool little bangstick, even in ammo conservation mode. So Caleb, the rumor is that USPSA is thinking about a PCC division. This begs the question: do magazine changes blow chunks on all of these little carbines? Will a reasonably talented IPSC’er with a 1911 or Glock always beat the snot out of a PCC guy on a classifier? There are some videos on Youtube of an HK sponsored shooter getting around 2.4 second shot to shot, with a magazine change. He had some MP5 variant.

    1. MP5s are hard to change the mags on. They insert and rock in. Newer carbines like the Evo and MPX insert and lock better.

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