Frame screw and thumb screw affecting mag's functionality

[bit-wizard]

I just diagnosed a problem with a friend's mag that he was building out of surplus parts from several gun trades that he'd done. What he has put together is an RT pro valve (level 7 bolt), a powerfeed automag body, some 3rd party AM/MM rail, and a benchmark frame (I think). The bolt kept sticking after each shot or so -- I had to push something up the barrel to reset it. I finally tried loosening the frame screw and thrumb screw in various combinations and hit on one that makes it work reliablly every time. It was frame screw 1/4 turn back from fully tightened and thumb screw 1/2 turn back from fully tightened.

So problem fixed, but I'd like to understand more about why the problem occurs in the first place. Can any of you who knowledge of this issue enlighten me please?

Thanks!
bit-wizard

[Tao]

I am not sure if this will help at all but here goes:

I have not done any modifications on my emag but I had a similar problem with the field strip screw needing to be tightened more than normally expected. I hand tightened it as tight as it would go but it would not pull the valve down enough for the sear to contact all of the time. So I would shoot and some shots would not trip the on/off pin or even short stroke the gun causing bolt stick since the valve was possitioned slightly too high above the sear.

Anyway it could be the way the sear contacts the valve...

[MoeMag]

hey there, check this out...



this is what happend to my ule body after making the field strip screw too tight, it shaved about a 1/16 of aluminum out of the body. I made the screw too tight it caused the valve to tilt up, with the pivot point being where the valve goes into the body. the bolt tilted enough so that it began shaving the body out. cool huh

[Shinyballs]

I had a problem with my rt mag, so I called AGD. ended up being the field strip screw. The tech told me to tighten it with an allan wrench every time.

[Tunaman]

I just had a couple of guns do this. I changed every single part on the marker trying to isolate the problem. What I came up with is the on/off assy is too tall, or the large on/off oring is too fat causing the on/off to stick out too far. Try swapping out the on/off assy for another or try a ult. If your rear field strip screw seems mushy when you tighten it, then you have the same symptoms...

[bit-wizard]

Thanks!

Thanks to each of you that responded for taking the time to educate me about this issue. It was certainly a challenging problem (for me anyway) to troubleshoot.

bit-wizard

[AGDlover]

yea if i ever get slight sticking of my bolt in a game when i come off i just adjust my back frame screw and no more problems