Just wanted to give a quick review of my experience with the Mean Arms EndoMag inserts. These inserts replace the internals of gen 2 or 3 30 round pmags. They allow your standard pmag to hold 30 rounds of 9mm. With the endomag you can use a standard AR lower receiver, eliminating the need for a stand alone 9mm lower.

The endomags have a LRBHO built into the magazine itself, which can be hit or miss with different 9mm builds. There was a tiny bit of break in with the endomag, but the company has YouTube videos detailing the process.

In the beginning I was have feeding issues, but it was due to the "ramped cone" on the barrel. Once I polished the snot out it, I've had no other issues. They just work!

Current setup is with a cheap 4.75in barrel, kak flash can, standard Anderson upper and lower receiver, Foxtrot Mike's 9mm Bcg and 6.4oz pistol buffer. I am completely impressed with this system and cannot recommend it enough. IMO the 9mm lowers look silly with stick mags, and retaining the ability to use multiple uppers on the same lower is exactly what I was looking for...After all, this modularity is one of the best features of the AR platform.