B5 Systems


The SIG MPX is a machine pistol. That’s right, a machine pistol even though it seems like a word we don’t use much anymore.


It combines SIG’s short-stroke gas piston system with the AR-style controls you are familiar with. Additionally, it can be set up to shoot 9mm, .357 SIG or .40 S&W. This is the MPX-K but barrel lengths and types of stocks can be swapped out to change the configuration at the operator level.


All told, there are four models: MPX-K, MPX-P, MPX-SD with integral suppressor and MPX-C.



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13 Responses to “SOFIC 2014 – SIG MPX”

  1. Luke says:

    Please tell me that VFG is keymod and will be sold separately.

  2. AbnMedOps says:

    Huh. Why a 4th Generation SMG, at this moment in history? If some costumer wants a suppressable pistol-caliber “machine-pistol”, why would they accept the addtional length and weight penalty inherent in this configuration, when they could shave off many inches with a 3rd Generation configuration (magazine thru the pistol grip, ala Uzi)?

    • Dan says:

      I could think of a few reasons, I think this sort of weapon has a specific audience in mind, I’m thinking police/military tactical group. Obviously this style/caliber weapon style/caliber is utilized over the M4 for its non-over penetration properties, however further to that I think this weapon has a place based on the following reasons:

      1. Transition across multiple weapon systems, by sharing a common layout, in this case the AR, the weapon training required to achieve a high level of competency across various weapons is reduced. In my own experience, we were required to learn both the MP5 structure and the M4, whilst not a big deal, sharing a common layout effectively turns what used to be 2 separate training continuum in to one, my expectation is that the end skill result would be more advanced given a similar training time frame.

      2. Use of a standard ammunition, obviously the MP7 is a fantastic weapon, however it does use its own ammunition, and this unfortunately makes it a harder sell to some agencies from various countries. Using a standardized ammunition type such a 9mm in this format provides a solution for clients looking for that option.

      3. As with the family of MP5 variants, the K is always utilized as a specialist weapon, say for a driver to use. However operating as part of a larger assault force, weapon and magazine compatibility is a big deal, therefore I would expect the K style to augment the use of the longer setup’s above.

      Overall for me, I can absolutely see some agencies showing interest in this product. It’s like most weapons and ammunition, they aren’t going to suit everybody’s needs, however some people have rules and restrictions they need to adhere to.

      • CAP says:

        It has been proven that light caliber rifle rounds actually have less of a risk of over-penetration than pistol rounds in an urban environtment. This is exactly why most every group who used pistol-caliber SMGs have mostly done away with them in favor of compact 5.56 rifles.

        I don’t understand why SIG is bothering with a modern SMG. I think their motive may be more for the civilian market with these. They could sell MPXs with no stock or foregrip as pistols and with that picatinny adapter on the end, an SBR conversion would be simple.

        • Dan says:

          I understand what you are saying about light caliber rounds and I am in agreement with you. However although I am aware that many agencies can purchase the required ammunition to achieve this, some other countries, like Australia, still have the ammunition restriction, due to the somewhat backwards nature of their military ammunition manufacturing. I am sure that Australia is not alone in this aspect, as such an updated variant of the MP5 style weapon, with AR ergonomics that fires a standard high production round that is currently approved for service does have a place in the marketplace, albeit perhaps a small one, especially in the US.

  3. Desert Lizard says:

    Agreed. I’m interested to see which situations professional organizations will use these in.

  4. straps says:

    Would be interesting to hear the insight of someone who’s fired this and an MP7.

  5. Joe says:

    Curious as to the application of .357SIG in this weapon. It would seem to me that it would be a good fit.

  6. Jack says:

    I think we’re past the point of a gun filling a specific role or several roles. You guys are missing the point.

    This thing looks like FUN!!

    Put a can on it and I bet there will be uncontrollable giggling. If the barrel/upper/stocks are all swappable, you’re going to have a lot of options if you go the SBR route.

    None of this stuff has to make “sense”. I’m in for a pistol in 9mm. What’s the thread pattern going to be?

  7. Bussaca says:

    SIG has been on a roll lately, anybody else notice they’ve been kicking over the hornets nest for the last couple months.. the sbp/pistol stocks, the flashider/silencer issue, the Picatinny railed tail cap for AR’s and a plethora of interchangeable snap on colapsable/folding stocks… everyone else see the tail cap on these and the Carbine they just put on SSD a couple days ago… I’m thinking interchangeable..

    Now if you can just buy the spring in receiver bolt assembly, vs the buffer tube assembly and drop it into you AR with their tail cap.. you got some real SBR fun in the works..

    GOD BLESS SIG at the moment.. Good for them.. I hope they corner the market.. or force others to diversify/R&D..

    It’s great to see some innovation in the field instead of carbon copy/ cookie cutter rifle clones.. You would have thought H&K would have beat everyone to the SMG market place with something like this instead of a 416, like a 416K 5 people can afford to own..

  8. Mohican says:

    Is this a come back to the HK MP5 style weapons?

  9. Bill says:

    There will always be a place for a pistol-caliber subcarbine or “heavy” pistol, if for no other reason than concealment and ease of transport, let alone zipping things like lightbulbs and meth lab pit bulls.

    Can I get it in rainbow titanium or truck tool-box diamond plate?