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Fire Control Unit – X01 for the SIG P320

The EXO ONE (X01) is pretty slick. It takes advantage of the SIG P320 Fire Control Unit (FCU) as a plug-and-play component. This multi-caliber exoskeleton accepts the FCU, barrel, slide assembly, and magazine release and can be configured in 9x19mm Parabellum, .357 SIG, and .40 S&W by transplanting the corresponding P320 components (.45 ACP is in development, as the changes in magazine well dimensions require a specialized lower receiver).


It features a non-reciprocating charging handle locks the action open (the slide to the rear) with an upward motion when fully retracted. The action can then be released with a downward motion (akin to HK-style weapon systems). In addition, if the charging handle is in the forward position, the slide can be released via the FCU slide release during reload procedures. The X01 features three M-Lok slots near the muzzle for accessory and grip attachments. The upper receiver features a 19-slot milspec M1913 picatinny rail.


Like the SIG MCX and MPX, the rear of the lower receiver features a vertical M1913 Picatinny rail to accept SIG MPX/MCX buttstocks and arm braces.

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22 Responses to “Fire Control Unit – X01 for the SIG P320”

  1. Marcus says:

    Interesting innovation. Glad to see people in the industry are still coming up with new ideas.

    I’m guessing since the XO1 does not reuse the 320 frame it is considered a legal “receiver”?

    • jdally says:

      I beg to differ… It’s only considered a frame. Just like you can swap put the entire body (upper and lower) of the P320 from full size down to subcompact and modify the caliber at will, the same goes with the X01. It is simply a chassis. The lower receiver is simply the trigger group essentially. It’s just an aftermarket frame for the P320 lower receiver.

    • Mike says:

      Bad guess.

    • random says:

      The trigger assembly on the 320 is the serialized receiver, so this is probably a non serialized accessory.

    • Curt says:

      The serialized portion of the 320 is the trigger module. So the receiver isn’t the part that requires an FFL transfer.

      The frame, or grip module, is interchangeable in order to allow users to change between various grip diameters, calibers, and barrel lengths. Additional slides are sold in kits that include a slide, magazine, and barrel in order to change calibers and change from full size to carry size to compact size while changing calibers.

  2. MIichael L McCollum says:

    The serial number on the P250 and P320 is the trigger group. Unlike all other pistols where the frame is numbered.

  3. MIichael L McCollum says:

    When where and how much? Ready to convert mine

  4. Dave says:

    Has this hit market yet ?

  5. B says:

    Looks a bit like a bloated TMP9.

  6. Mike says:

    If reasonably priced,I’m in.

  7. PTMcCain says:

    Does it go off when you drop it?

  8. Silleme says:

    Very interesting. When can I get my hands on one?

  9. Alex says:

    Sooo, basically a Roni system for the Sig? Nice..

  10. David says:

    Interesting concept. Don’t drop it….

  11. Bad Dancer says:

    Interesting. I am curious what suppressors will fit inside this or what clearances it has for such.

  12. RobHWood says:

    Since this is the Fire Control Unit accessory will it work for the Sig P250 as well? If so it would greatly increase the possible target market. I have a few P250s with no plan to move up to the P320.

  13. Luke says:

    This looks awesome, and a logical place to go with the serialized trigger group.

    I was a bit bummed to see it use the slide though, was hoping for a longer fixed barrel and blowback.

  14. Z Thomas says:

    Looking to purchase a p320 fire control assembly. Name your within reason price.
    Thanks Z Thomas