Stern Defense AR-15 Conversion Block for Glock 9mm and .40 S&W Magazines

Manufactured by Stern Defense
Manufactured by Stern Defense
2 Reviews

In Stock

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The Stern Defense Magazine Conversion Block allows you to use 9mm and .40 S&W Glock magazines in your favorite standard AR-15 lower receiver. This magazine adapter installs in seconds and features last round bolt hold open functionality – a welcome improvement when compared to other PCC builds. The Stern Defense Mag-AD9 adapter is constructed from 6061-T6 aluminum with a 4140 steel NiB coated feed ramp and are designed to be used with a Glock cut bolt. If you are looking to convert a standard AR to use 9mm or .40 caliber, this mag well adapter is a perfect start.

  • Designed for use with 9mm or .40 caliber barrels and Glock cut bolts
  • Constructed from 6061-T6 aluminum with type 3 hardcoat anodized finish
  • 4140 steel NiB coated feed ramp
  • Ergonomic magazine release
  • Last round bolt hold open
  • Works with all generations of Glock magazines
  • Works with any Mil-Spec lower receiver
  • Made in the U.S.A.

With pistol caliber AR-15s on the rise in popularity, Stern Defense is leading the way with innovative components to convert your standard AR lower to be compatible with pistol magazines from Glock, S&W, and even Beretta in a variety of calibers. Stern Defense is located in Missouri and dedicated to helping you build the ultimate pistol caliber carbine.
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BrandStern Defense
Fitment9mm or .40 Glock Magazines

WARNING: This Product can expose you to chemicals which is known to state of California to cause Cancer and Reproductive Harm. For more information, see

California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to

Ratings & Reviews

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Great 9mm conversion. A must for an AR owner who wants to shoot and train with cheaper ammo

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Works as advertised, just follow instruction for lower install( Literally installs less than two minutes and comes off less than that). Ran with my few KCI mags and ran with no problem and BHO worked. Occasionally bolt will not hold open but narrowed it down to the same glock magazine(gen 3). Used with a FM 16” upper with red dot combo (Kit-FM16-9MM-3-MB-MD-RBGII) and ran great. For some reason Glock gen 4 mags will not drop free but my old KCI will( I got lucky).Lefty here so mag release works out to my advantage. A bit pricey but cheaper than getting a dedicated lower and have it registered.

Awesome adapter


I’ve ran at least 1000 rounds of Winchester target ammo with aftermarket and OEM glock mags. This adapter is flawless.