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Joined:
Feb 2026
Posts:
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WI, USA
Posted: 2/8/2026 7:36:24 PM EDT
[Last Edit: Hook-n-hunting][Edited]
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I recently finished an 11.5. Aero m4e1 upper/lower. Toolcraft dlc bcg. Geissele super 42 w/h2. Pre cut trigger that is included with the selector. Rhino x whisper pickle I went to the range to function check my arc fire. Safety functions properly. No catching up of anything with the bcg on both semi or ss. The issue is in semi, I can fire a round, bolt cycles, ejects, loads a new round... then nothing. The hammer seems to not be locking back. So I have to charge it maually to lock the hammer back which results in it ejecting a new round. I thought, okay, gas or buffer weight issue. But in ss, it functions just fine. Even checked for bolt hold open I'm by no means a pro at gun troubleshooting and this is the first ar I've assembled completly from scratch. It could be I'm just an idiot but any thoughts or solutions would be much appreciated. |
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In forced reset, Either problem with trigger force reset happening with the carrier too far off the face of the receiver extension, so when you do pull the trigger again, bolt is not close to lock up, and Tail of bolt stlll in side the carrier to block the FP when hammer strikes it (to prevent out of battery ignition of the round). Or, Timing on reset may be fine, but you have bolt bounce going on, with tail of the bolt back inside the carrier to do the same. If problem is in semi (not force reset mod), then disco not retaining the hammer correctly when trigger is held back, and hammer is riding the carrier back down, instead of being retained by the disco until trigger is release for hammer reset. In the later, leave the trigger untouched, cock the hammer back until its rear hook is just about as close as you can get to the disco hook, and check the free gap between the two. The free gap between the two should be about .003 (thickness of a sheet of copier paper, and if gap is too wide, then may need to smith the front/bottom of the disco surface (where it rides on the front top of the trigger), to decrease the free gap back to .003" Note, instead of having to measure free gap to start with, you can shotgun the upper open, pull the trigger back, cock the hammer to the dis connector f trigger held back, then with your hand in front of the hammer so it does not crash to front of receiver void wall, slowly release the trigger. The disco should release the hammer when the trigger is dam near all the way forward back at is home rest position, with the hammer front seat catching the hammer/not early disco sear release of allowing it to keep going with front of trigger sear out of position, so hammer crashes into your hand off the disco release. |
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'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
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'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
Joined:
Feb 2026
Posts:
2
EE: 0% (0)
WI, USA
| Thanks for the response. I'm going to be honest, I don't totally grasp what you're suggesting. I switched out hammers and it still wasn't locking back on semi with the trigger pressed which makes me think the trigger that was sent with the arc is not quite to spec. I have some extra triggers laying around. Ill Drexel one out to see if that helps. I did notice one prong of the trigger spring at an offset. Regardless, thank you for the advice |
Joined:
Feb 2026
Posts:
3
EE: 0% (0)
WI, USA
| Appreciate the response. I'm going to be honest, I don't totally grasp what you were suggesting. I switched out hammers and it still wasn't locking back on semi with the trigger pressed which makes me think it wast he trigger causing the issue. I noticed one of the prongs on trigger spring was bent in an offset. Switch it out and it seem to work now. I'll know for sure when I take it back to the range. Thanks for the advice. |
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Hey, I have an AS Designs ARC-fire MP5 lower that I paired with a PTR-5RS upper. I know you've got an AR trigger, but this is basically an AR trigger inside an MP5 lower made for the purpose of using an AR trigger with the MP5. So it's basically the same trigger you're using. Anyway, I had similar issues with function. For me it came down to the precise left-right spacing of the selector. You probably need either one or two shims, or a different cam, or both. Work directly with the AS Designs support people. They helped get mine working. It will take a little time and you may have to send videos to show them what's happening. |
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