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CMMG MK4 PDW Upper Receiver 300 Blackout 8"

  • The Mk4 PDW Upper Group is CMMG’s smallest, most compact upper group equipped with the RKM7 KeyMod free floating hand guard and a nitrided 4140 CrMo steel barrel. Every upper group is covered by CMMG’s lifetime quality guarantee.

    *Please be advised that our system will prevent products from being shipped to locations where they are prohibited by law. Both your billing and shipping address must be located in an area where these items are not prohibited*
  • Caliber: 300 Blackout
    Barrel: 8.0”, 1:7 twist, medium taper, 4140CM, SBN
    Muzzle: A2 comp., threaded 5/8-24
    Hand Guard: CMMG RKM7 KeyMod hand guard
    Receiver: Forged 7075-T6 AL M4 type upper
    Gas Port Location: Pistol

    Upper Group consists of:
    Upper Receiver Assembly (Upper Receiver, Ejection Port Cover, Forward Assist)
    Barrel Sub-Assembly
    Hand Guard and Barrel Nut
    Charging Handle
    Bolt Carrier Group
  • The MSR Arms Advisor articles are intended to answer some of the most common shooter questions and assist our customers in making the best purchasing decision possible.
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  • No questions have been submitted regarding this product. If you have a question regarding this, or any of our other products, please submit them by emailing We will return your email promptly and post both the question and answer here for our other customers to view. Remember, there are no dumb questions... Thank you, MSR Arms

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