how high is the little nub that catches the mag on your mag catch?
my ameetec built cav lower is dropping the mag every couple of rounds.
i called cav and they suggested removing the flashing from around the mag catch.
i did that, but i’m trying to figure out if my mag catch is out of spec… 
In the long term you would be better served by upgrading your lower to an in-spec lower receiver. LMT comes to mind and there are many members here who have had great success with their products. Grant at G&R Tactical would be the man to contact should you decide to go that route. I may be most comfortable with Colt for my fighting rifles but LMT is on my to-do list without any reservation.
yeah i just dropped like 950 on this rifle.
putting another 400 into it is not on the list.
are you telling me that a cav lower can’t be made to fire more than 2 rounds without dropping the mag?
Check out the thread Pmag and Lower problem!!. If the problem with the lower is that the mag catch is too high then you will most likely be out of luck. If the problem is related to the horizontal (in and out) position of the catch then there is some room for error and adjustment.
i think it’s an in/out problem
i gently tweaked the slot in the mag a little too. i wish i had though of that at the range it probably would have solved everything.
a full mag seats fine, stays in fine. this is a molded poly lower, so i highly doubt the pocket for the mag catch is in the wrong place. if it was there’d be thousands of guns with the same problem.
The actual protrusion on mine measures .058"
thanks… mine is .048.
i wouldn’t think thta would cause too much trouble…
Is the Mag catch adjusted properly? Maybe try turning up the tension a few notches?
Exactly. The threaded portion of the catch should be flush with the button.
i got it working perfect today. i think the flashing was the problem. 
feeds my 2 USGI 20 rounders and my poly mag perfect. 