The Mean Arms EndoMag makes a big claim. They say their magazine insert converts your Gen 2 or Gen 3 5.56/.223 PMAG® housing into a 9mm magazine to use with a standard AR lower and 9mm upper.I have been shooting one all week, they work, every time.
Millions of you guys bought an AR lower back during one of the panics. If you have a lower and a Magpul magazine sitting around, $29.99 and a 9mm upper will turn it into a training gun that uses mags the same size as 5.56 mags. The mags can be converted back to 5.56 in seconds.
Do you live in a state where your freedom is regulated? No worries. The Endomag has a built in tab which limits capacity to 10 rounds. It is marked at 15, 20 and 30, you can cut the tab to fit your circumstances. You can always increase the capacity up to a maximum of 30 with a pair of wire cutters.
All the AR controls work just they way they are supposed to including last round bolt hold open and they fit in your mag pouches. No more dedicated lowers, EndoMags work with Glock or Colt variant 9mm Bolt Carrier Groups. They even have a version that works with the CMMG Guard uppers.