Works pretty good, expensive, worth it
** Do anything in this review at your own risk ** I was looking at the pros and cons for this device, and I was thinking that this device is not aesthetically pleasing because it sticks out of the mag well a bit, it is not overly easy to install as it took me 3x to get the insert adjusted to what I think is right, it cost me $180 with my edge membership so I wouldn't say it is particularly cheap but it does serve a purpose, so far it has been safe, it has been tough so far, and it ONLY works with ARs with a GLOCK-CUT bolt--it will NOT work without a GLOCK-CUT bolt. It takes a little bit of fenagling to get the mag release catch on the AR and this insert aligned properly. Don't forget to loosen ALL of the set screws on this insert BEFORE you try to install it in your AR. The screws have some semi-locking compound on them or they are pretty tight, but don't freak out when you are working on the insert. If you take it slow and easy, you should be fine. If you install the insert up too high or too low, the INSERT mag release may bind on you. It is located on the bottom corner of the insert, and you will need to get used to it compared to a normal AR mag release. In my experience, my AR mag release lever on the left side of the AR needed to be aligned about dead center. If you buy one of these, you'll know what I'm talking about. Those little nylon-tipped set screws take some finesse to get them right. ALSO, Glock factory mags WILL work in this insert, BUT you need to check the side of your Glock factory mag for the little triangle in the mag catch slot. If you HAVE the triangle, my advice is DON'T use that mag with this insert. Why? Because the little triangle causes the Stern Defense INSERT mag catch to not fully seat in the mag slot, and you risk having your full or partially-full mag dropping out of your AR while in use. I bought (20) 17rd PMAGS and I carry a Glock17 as my primary sidearm to go along with my AR 9mm, so I can use my PMAGs in either one. I am not paid by Magpul in any way for this review, but I did decide not to use any factory mags that have the triangle, and currently I am using PMAGs exclusively. Good luck.
Best solution for the 80% crowd
I've bought 2 of these now, in the middle of the second build. The first one fit like a glove with an 80% lower and a PSA Gen4 upper. I think I have a dedicated 9mm buffer in that one and it has performed flawlessly with a 23,27 and 32 round mags and cheapo ammo. Second one was really tight in the mag well of two different lowers, but it does snap into place with a little effort. Next step is to see how it does with subsonic ammo.
Not perfect but close
This adapter is fantastic. The pistol I used fed reliably from all the Glock mags that fit in the well, including 40 S&W and 357 SIG magazines. Installation and adjustment is a matter of turning in one screw to set it, and then two more for standoffs so it doesn't move around when you seat a new magazine. The only reason I took off a star is because the mag release is a little awkward to use, the thing was very sticky with an aftermarket 9mm drum magazine, and the bolt hold open was a little hyper aggressive and held the bolt open with one still in the magazine.
Reliable
Building a 9mm AR Carbine on a budget can quickly become an expensive endeavor if you buy unreliable parts. The AR-15 9mm Conversion Adapter for Glock Magazines by STERN DEFENSE Is a reliable way to use Glock magazines in a Mil-spec lower. I use it for USPSA PCC division and Steel Challenge matches to keep the feel of an M-4 and for training. Ive personally tried other methods and this system is far superior. The feed ramp angle on 9mm is critical for proper function and reliability, with the vast array of projectile profiles. So far Ive had luck with multiple types of 9mm projectiles I.E. Winchester 124gr FMJ, 145gr RN Bayou, and 147gr FP/HP Berrys. The last round Bolt hold open is somewhat unnecessary for PCC, however, is great to feel the weight transfer of the bolt carrier group and buffer and have it lock on the last round. The only feature that I dislike is the magazine release is located at the bottom of the unit which is not a big deal if your state allows standard capacity magazines. However, Id like index the same magazine release in the same configuration of an AR series firearm, which would be difficult without permanently modifying the magazine. Overall a great product the moment you open the package you can see that a lot of thought went into its development and manufacturer.
