At the last Big 3 East we met the great folks at Stern Defense. They have only been in the industry for a few months and showed off their Glock magazine adapter for use in Mil-Spec AR-15s. We got one of their MAG-AD9 and 9mm upper in for review.

Not All Glock Magazine Adapters Are Created Equal

There are only a couple of magazine adapters that use Glock magazines in a 5.56 AR lower. Torkmag and ATI come to mind. The Torkmag adapter is a two-part adapter that is more like two wedges inserted into the 5.56 mag well. You also need to modify your Glock magazines and cut a new mag catch notch into the side of the mag body. ATI has a self-contained unit but it does not look robust. For example, the bolt catch activator is a bent piece of wire.

The Stern Defense MAG-AD9 is machined aluminum with a 4140 NiB coated feed ramp. The bolt stop lifter uses a rolling actuator for mechanical advantage to help lift the bolt catch. So even if the Glock magazine spring is weak, it will still be able to lift the bolt catch on the last round fired.

On the other side of the MAG-AD9, the design of the mag adapter has a shelf that the mag hits against to prevent over insertion.

As an added over travel mag stop, the feed ramp hangs just over the leading edge of the magazine body.

The MAG-AD9 has a built-in magazine release/catch.

 

You can see the mag release button at the bottom corner.

Releasing the magazine does take a little getting used to. I have made the mistake of trying to push my extended AR Mag release.  I think using something like a bullet button would actually be useful so you don’t accidentally press the mag release if you intend on making your AR a dedicated 9mm carbine.

Installing the MAG-AD9

Pressing the AR mag release is not necessarily a bad thing. The MAG-AD9 actually uses the AR mag catch as a shelf to help position and hold the adapter in place but there is a Delrin block that wedges the adapter into place. So pushing on the AR mag release would not cause the adapter to suddenly fall out of the mag well.

To install the mag adapter you simply insert it up into the mag well like an AR-15 magazine. On the leading edge of the mag adapter is a pivoting Delrin block. You tighten the screw at the bottom of the adapter which then pushes the Delrin block forward and wedges the adapter inside the AR magwell.

Make sure you are pushing the mag adapter down as you tighten the Delrin block screw, then you tighten the two set screws on the left side of the adapter. These set screws just need to touch the bottom of the AR mag well. This prevents the adapter from shifting upwards as you slam Glock magazines up inside.

Back at Big 3 East, I recommended to Stern Defense that their MAG-AD9 needed a flared magwell. The hole for the magazine is rather narrow and there is not a lot of room for error when inserting the magazine. While there is a hint of a bevel, a mag funnel would go a long way, especially for competitive shooters.

A month after Big 3 East, Stern Defense released a bolt on Delrin flared mag well for the MAG-AD9.

Here is a comparison of the MAG-AD FLARE with a factory mag well for an STI Steel Master race gun. 

There is a cutout for the magazine release.

SD 15 INCH MOD4 MLOK 9MM Upper Reciever

Stern Defense also sent in their 16″ bbl 9mm upper receiver. It came with a 15″ M-LOK free float handguard. There are a couple of nice features they added to this upper you don’t see in other uppers.

The BCG is coated in Nickel Boron making it super easy to clean.

Their free float handguard has two small extensions to keep it aligned with the upper receiver and prevent rotation. Surprisingly these extensions are machined into the handguard. I have seen something similar in my Angry Gun Wire Cutter Rail LVOA style handguard. However, the anti-rotation tabs were separate pieces and plugged into the back of the handguard. Their tabs are made of steel though whereas the Stern Defense tabs are part of the handguard which is made of 6061 aluminum.

Stern includes an oversized charging handle. The texture is actually more aggressive than I anticipated.

The Stern Defense upper came with a forward assist. However, the bolt carrier does not have any side serrations like a regular AR-15 bolt carrier so it is useless. I removed it to see if I would experience gas blowback when I ran it suppressed. To my surprise, I did not experience any gas to the face.

At the other end of the upper is the Stern SCB 9 compensator break. I did not really notice much of a difference with or without the muzzle brake.

There are QD sling holes machined into the front and rear of the handguard.

Shooting the Stern Defense Adapted AR

When I was down at Big 3 East, Stern Defense had their uppers on select fire lowers. I originally used my carbine buffer and did not experience any issues. They recommend using an H3 buffer so I tried one and it made a difference. It cut the recoil down a lot.

Just this past weekend I got chance to shoot a USPSA match with the Stern Defense adapter AR. I haven’t shot a match since last year so I was a bit rusty but had a blast. The Stern Defense upper ran flawlessly and the mag adapter worked.

The mag flare came into play on one stage where we had to start with the gun on a table, shoot either 4 paper targets or 8 pieces of steel. Perform a mandatory reload and shoot weak-handed at the other array of targets. The flare helped make the magazine reload effortless. Unfortunately, I do not have any footage of this stage.

Final Thoughts

I have played with several different 9mm carbines. The MP5 is probably my most favorite but the cost is a bit much. I even bought a Palmetto State Armory and built a 9mm AR pistol however it’s reliability is hit or miss and while I am sure that is my fault, 9mm AR builds can be finicky. The Stern Defense setup is simple and drops right in. No modifications are needed and you can convert your AR-15 into a 9mm carbine that feeds with Glock mags. They also have adapters to use M&P magazines as well as adapters for Beretta 92 magazines. I heard they are working on a Sig P320 mag adapter soon and they have an adapter that uses M&P45 magazines for those who want a .45acp carbine. One big benefit to using their mag adapter is if you have a transferable select fire AR or an SBR AR. Now you can simply caliber convert them with the Stern Defense MAG-AD9 and a 9mm upper. Now you have an NFA 9mm sub gun and you did not have to file another form 4 or pay the tax stamp. The MAG-AD9 retails for $179.99 while the upper is on sale for $490.05. If you want the flared Delrin mag well then add another $73. While you don’t need to use their upper receiver, I highly recommend the mag adapter and flare. You can then use almost any 9mm upper you want but I don’t think they will be feature packed for the money like the Stern Defense complete uppers. I was told that Stern Defense is working on a new bolt carrier design that will be compatible with the Law Tactical Folder. So stay tuned for that info or check out their website for more info.