Polymer 80 V3 FCG issues:

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  • tallen702

    Ultimate Member
    MDS Supporter
    Sep 3, 2012
    5,102
    In the boonies of MoCo
    So, I just got a Poly80 v3 5.56 80% lower in today and got to milling everything out. I previously milled and built a G150 5.56 lower from them and haven't had any issues what-so-ever with that build.

    So, when I put everything together on this V3 lower, I was dismayed to find that the fire control group just doesn't work.

    I got a PSA LPK and everything went together fine. The issue is that when cocked, the interrupter won't disengage, preventing the hammer from returning to the ready position. If I push down on the back of the interrupter, the it will disengage, but there isn't enough clearance with the safety selector to allow the trigger to trip the hammer.

    I pulled the FCG out of my other AR lower and put it in the V3 I just finished milling and got the same issue with the interrupter, but when I manually disengaged it, I did not have a repeat of the safety issue as there was enough clearance to allow the trigger to trip the hammer.

    I'm stumped. Everything is milled out correctly. The pin holes were properly drilled, etc. etc. I know I can shave some material from the flat on the PSA selector to achieve the clearance and solve the hammer trip issue, but that still doesn't necessarily solve the disconnector problem.

    Anyone have any ideas? Thanks!

    ---------------edit----------------


    After pulling out some feeler gauges and calipers, it seems like the jig mis-positioned the right-side trigger pin hole about .25mm lower than the left-side which is preventing the rear of the trigger from dropping low enough to fully re-set and disengage the disconnector. Emailed Poly80 about it. We'll see how good they are with their warranty since the bit didn't drift AT ALL during the drilling process for the pin holes. There's literally no marring at all to the guide holes on the jig.
     
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