u/eric69cam

Just picked up this MPX (my first PCC) from a local online auction. Learning a bit more about the operating system, accessories and so on. Excited to get to shooting it soon.

I am puzzled by one detail thought that I’m not having much luck in finding in videos of takedowns or reviews etc. The lower receiver has a button high and to the rear, right in front of the side-folding brace mount. Can anyone advise what it is and its function?

Any other details, generation/model/options you know just from the photo would be appreciated.