The ARMS 40L that I had rocked quite a bit and if sand got in the spring it wouldn't fully engage upright.
The PRI gas block version I saw was the worse, it would almost flop side to side.
I now use Troy flip up's and Daniel Defense fixed, these are not High Power Match sights, they are decent BUIS's. I can make A zone hits out to 300 yards. I never cared for the sight picture of the Magpuls but they were useable.
