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Stern Defense Smith & Wesson M&P 9mm / 40 Cal. Magazine Adapter for AR-15

  • With the Stern Defense Mag-ADMP940 adapter, you can easily convert your AR-15 into an AR-9 or AR-40. Unlike other magazine well adapters, the Mag-ADMP940 is made from lightweight 6061 T6 aircraft grade aluminum which means it’s built for longevity and reliability. With premium features like last round bolt hold open (LRBHO) and an easy to reach mag release, the Stern Defense Mag-ADMP940 is the only choice for an AR-9/AR-40 conversion!

    • Installs quickly, easily, and most importantly, securely into any mil spec AR-15 lower receiver.
    • Designed from the ground up to work with AR-15 and M16 mil-spec upper receivers.
    • Made in the U.S.A.
    • 4140 NiB coated feed ramp.
    • Hard coat anodized type 3.
    • Sturdy Construction.
    • Works with all generations of Smith & Wesson M&P 9mm & 40 Cal. magazines*
    • Requires 9mm or .40 S&W. barrel and Glock cut bolt*
    • *See Specs tab for more information
    • See Media Tab for install video.


  • Manufacturer Part Number: MAGADMP9&40

    Not compatible with PSA Hybrid or Foxtrot Mike bolts. This is due to the lug which strips a round off of the magazine being .035 of an inch further from center-line as compared to other bolt systems.


  • 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.
  • 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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