I just bought an MPX Gen 2 made in Jan 2017. I shot a couple hundred rounds as from the factory then sent the barrel for chopping. I received my barrel back from class III machining. I got that cut down to 6 inches, and got them to install my 3 lug adapter made by In Lead we trust ($75 for the work). The suppressor I used was a rugged 45 with a 9 mm end cap and a three lug adapter. I also have a SB tactical arm brace stock installed.
The ammunition I used was LAWMENS 147gr TMJ sub sonic, Freedom Ammunition 115gr, PPU 115 grain FMJ. I DID NOT open up the gas port in the barrel.
First I shot the rifle with no suppressor. All of the ammo fired/cycled with no issues. Then I installed the suppressor and shot another 200 or so assorted rounds of the above ammunition. Had not one issue at all. Also, I was using mostly Gen 1 magazines (4). I had one Gen 2 Magazine. All worked fine. All magazines were tested full.
Next is a binary trigger....I have to do it now )))