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  • Colt m16 9mm SMG lower with a CMMG mk9 upper?

     Noderly updated 1 week, 5 days ago 2 Members · 2 Posts
  • Noderly

    May 15, 2022 at 12:26 am

    Anyone know if there’s any fitment issues here on these? Looking to potentially procure a full auto mg but I really dig CMMG’s radial delayed blowback system and figured it would be nice to swap in a new upper.

    EDIT: For others that search this in the future: I did hear back from CMMG a few moments ago, and they mentioned the newer 9mm uppers with RDB dont work with the colt m16 9mm smg lowers. They DO work with the older 9mm, direct blowback uppers — so I would have to give up the RDB if i wanted it to work.

    Sounds like an M16 5.56 lower with converted mags is a better deal for flexibility.

  • Mr-Heckler

    May 15, 2022 at 12:27 am

    I have a Colt M16 lower (not 9mm) and a CMMG Mk9 upper that work well together. I just added the upper and it worked without adjustment. I use EndoMags for mine. You might have a harder time sourcing a 9mm Colt SMG lower than a regular Colt M16 lower due to numbers produced and transferable. Also, the M16 lower is more versatile since it can readily accept 5.56 magazines.

  • lapdogma

    May 15, 2022 at 12:27 am

    C3junkie from has a long thread and this website reviewing it.

    AR15 / M16 Info

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