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001-SD MAG-AD-MP-9AND40/P320-M


* NOTE: The new Sig 30 rd magazine is NOT compatible *

Convert your standard mil spec AR 15, M4, M16 lower assembly to use 9mm and .40 S&W M&P and P320/P250 Magazines!  The Mag-AD series adapters install in seconds.  Boasting a last round hold open feature making them a breakthrough product and a must-have for law enforcement and civilian gun enthusiasts alike.

The Stern Mag-AD series adapters are made of aircraft grade aluminum, lightweight with ergonomic design.   

Note: These adapters require the use of a 9mm or 40S&W barrel, "depending on chosen caliber" and a Glock cut bolt.


Already have a Colt Style bolt and want to use our system?  We have you covered.
Click Here

Don't Have a bolt, want one?  We have you covered.
Click Here

Don't Have a barrel, want one?  We have you covered.
Click Here


Technical Information:

⦁    Made in the U.S.A.

⦁    Constructed from 6061 T6 aircraft grade aluminum.

⦁    4140 NiB coated feed ramp.

⦁    Hard coat anodized type 3.

⦁    Sturdy Construction.

⦁    Ergonomic mag release.

⦁    Works with all generations of M&P magazines.

⦁    Works with P320 and P250 magazines

⦁    Works with any mil spec ar15 lower receiver.

⦁     All gun components besides the Bolt and Barrel remain stock

Please visit the following link before purchasing to ensure compatibility with your setup.


5 Reviews Hide Reviews Show Reviews

  • 5
    High Quality Manufacturing

    Posted by Ernesto on Feb 14th 2022

    Awesome! Works with P320 Legion mags and ProMag P320 mags.

  • 5
    P320 9mm adapter

    Posted by Barry on Jul 9th 2021

    LOVE IT! Quality, installation, function, all great. Tested endomags first...ugh.

  • 5
    Quality product that functions

    Posted by Brian Harris on Jan 23rd 2020

    im super pleased with how well my sbr runs with this! the only thing i could ask for would be the logo cut in during the milling process and then anodized so i dont have the "nascar" branding. but if thats all im complaining about, this earned the 5 stars. Also the Glock cut for basically free shows this company know how to take care of a customer.

  • 5

    Posted by Brent Janzen on Nov 26th 2019

    The MAG-ADMP9&40 performs very well. The magwell adapter installs in seconds, and is very secure in my M&P15T lower. Only a few misfeeds, but more likely caused by the Promag M&P 32rd clips not being broken-in. Thanks Stern Defense.

  • 5
    Awesomeness defined!

    Posted by Ranger Doc on Oct 28th 2019

    Purchased this as part of the basic build kit. Using in an Aero Precision lower. The device works perfectly and the design is great and simple to use. I did have to do some minor fitting on my Aero lower. When installed, the magazine release would not function. The part that extends upward to engage the magazine's notch was rubbing on the inside of the mag-well of the lower. When examining the lower I could see that the broach cut for the mag-well left a small layer of extra material at the front side of the mag-well. I simply filed this down so that the entire side of the inside of the mag-well was level and smooth. This fixed the issue completely. NOT a fault of this product at all, but likely a common issue with tight fitting mag-wells.