Not getting bolt lockback when suppressed

[LMT/556]

My problem is most consistent with Okay 20 round mags. Okay 30s and Magpul M3 30s mags lock back fine. I use 20 round mags shooting prone.

[Pappabear]

You didnt try Vltor A5, it remedies this problem for me. I now I'ma broken record, but all my guns have A5's and all run great suppressed.

PB

[LMT/556]

I tried to compare two ambi lowers and one defender without getting consistent measurement of bolt catch height, but I've included pics of all three in the link provided, held up with an Okay 20 round mag. I can't tell much difference between my samples, and I'm inclined to believe the added weight/resistance of the right side ambi controls is the culprit.