Flawless and worth every penny - Stern Defense MAG-AD9 AR-15 Glock 9mm/.40 Magazine Conversion Adapter

I purchased this mag adapter and the Stern Defense 9mm upper as my first foray into 9mm PCC builds. I plugged the two parts onto a random 5.56 lower, took it to the range, and it was an incredibly fun experience. First of all, installation time was minutes. All tools were provided though the instructions needed more clarity. It did take a while to figure out how to use the mag release but once I realized it worked using an index finger push release OR thumb release a-la-H&K MP5 style, the release became very fast and instinctual to use. The bolt hold open feature is freakin' awesome as it did not change the way I shoot ARs. At 50 yards with a 1.5X ACOG and ETS 32 round mags, I was putting lead on a steel plate for 400 rounds with no failures (although one of my ETS mag springs got bound up and failed to feed). And I was running the gun practically bone dry! The adapter feeds flawlessly with factory Glock mag and Magpul 20 round mags. I also put 20 rounds of hollow points through this and again no problems. The only malfunction was the aforementioned janky ETS mag spring that bound up. Not the adapter's fault. My only complaint is how dirty the gun gets. Definitely disassemble and clean the adapter after shooting. Other than that, three thumbs up for this clever little adapter!