Mag-AD 9mm / .40 S&W Glock Magazine Adapter

Revolutionizing AR Builds. Designed, Machined, and Assembled in Our Factory.

The Mag-AD 9mm / .40 S&W Glock Magazine Adapter is Stern Defense’s flagship product, the one that put us on the map. Trusted by law enforcement and civilian gun enthusiasts alike, this adapter allows you to quickly convert your standard mil-spec AR-15, M4, or M16 lower assembly to accept Glock 9mm and .40 S&W magazines.

Crafted entirely in-house at our factory, every aspect of the Mag-AD is meticulously designed and built to ensure superior performance, quality, and precision. The adapter boasts a last round hold open feature, a breakthrough innovation that elevates the shooting experience—making it a must-have for anyone looking to enhance their AR build.

✅ Why Choose the Mag-AD?

Quick Installation: Installs in seconds, transforming your AR-15 lower into a 9mm or .40 S&W Glock mag-compatible firearm
Last Round Hold Open: A critical feature for reliability and functionality, ideal for both law enforcement and civilian use
Lightweight & Ergonomic: Constructed from 6061 T6 aircraft-grade aluminum for optimal performance and comfort
Durable: Features a 4140 NiB-coated feed ramp and Type 3 hard coat anodization for wear resistance

⚙️ Technical Information

Material: Constructed from 6061 T6 aircraft-grade aluminum
Feed Ramp: 4140 NiB-coated for durability
Finish: Hard coat anodized Type 3 for maximum wear protection
Mag Release: Ergonomically designed for ease of use
Compatibility: Works with any mil-spec AR-15 lower receiver
Bolt and Barrel: Requires a 9mm or .40 S&W barrel (depending on caliber) and a Glock-cut bolt
Stock Components: All components remain stock, except for the bolt and barrel

⚠️ Important Notes

Buffer Requirement: Must be used with a 5.4-ounce buffer or heavier when using a carbine spring with 9mm and at least 7.5 - ounce buffer with 40SW
Click here for the recommended buffer
Compatibility Check: Be sure to check compatibility with your setup before purchasing.
Click here to confirm compatibility

✅ Looking for a Complete Conversion Kit?

We’ve got you covered with everything you need to get started.

Transform Your AR Build Today

The Mag-AD 9mm / .40 S&W Glock Magazine Adapter is more than just a product—it’s an essential upgrade for anyone looking to get the most out of their AR-15 build. Whether you’re in law enforcement, competition shooting, or a civilian enthusiast, Stern Defense brings you the best in quality, performance, and reliability—all crafted right here in our factory.

57 Reviews Hide Reviews Show Reviews

5
MAG-AD9

Posted by H Allen Davis on Feb 24th 2022

I've built several dozen AR platform rifles and pistols over the last decade, many of them as PCCs. I've now built two 9mm AR-15 pistols using the MAG-AD9 adapter, and for my money, it's the absolute best way to go, no doubt. The Stern Defense adapter is far superior to all its competitors, too. The thing is not just well-built, it's rugged in the extreme. Using this adapter in a standard AR-15 lower gives you the flexibility to keep your AR-15 instantly ready for use as a conventional caliber weapon, be it a 5.56mm, .300 BLK., or any other chambering. This is a huge consideration for folks who are limited in only being owning a single AR rifle or pistol. In addition, the last round hold-open is drop-dead reliable, too (and if yours doesn't work, blame the magazine). The MAG-AD9 is the best way to go no matter what, even if you intend to use your weapon as a dedicated 9mm rifle, carbine or pistol.
5
Mag ad9

Posted by Eric on Jan 18th 2022

Awesome build quality. Have ets 32rnd Glock mags which fit/ function perfectly. Zero complaints, would recommend
5
Awesome Product

Posted by Sok Chun on Dec 6th 2021

So far is the best conversion block than others, Thanks Stern!!
5
purchased with 9mm upper

Posted by Col.451 on Nov 29th 2021

Excellent quality and am headed to range this week with it. Pricey but you get what you pay for. Fit and finish superb and the shorty upper is exactly what I've waited for.
5
Extremely well made

Posted by Frank Perreault on Nov 14th 2021

I was very happy with the build quality. It installed in the gun with no problems and worked like a charm. Couldn't be happier!
5
Ar-15 Mag Block for 9mm

Posted by Gregory Lee on Oct 13th 2021

This is a very high quality piece of equipment that works flawlessly. I will be purchasing another.
5
MAG-AD9

Posted by Deez N. on Oct 9th 2021

Solid construction and flawless function. Works perfect with the psa gen4 9mm upper. No jams or fuss with ets glock mags. Would definitely reccommend.
5
Ad9

Posted by Steve on Aug 3rd 2021

No brainer. If you're unsure of this product then you haven't been paying attention. Buy it. If you buy a dedicated lower it most likely won't have last round hold open
5
AR mag adapter 9mm/40 s&w

Posted by Marion D Richardson on Jul 27th 2021

Works great for 40 cal. Carbine and no malfunction after 500 rds, if you want to build a pcc this is the magwell adapter you need.