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Posted: 1/17/2010 4:07:20 PM EDT
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While doing an assembly of an AR-15 lower yesterday, during the FCG test dry fire, the hammer would latch to the trigger during cocking when the trigger was not held back as one would do when first charging the gun. However, when the trigger was pulled and held back as one would do during normal semi auto firing, and then the hammer was cocked to simulate the bolt moving back the hammer would catch in the disconnector as it should but would slam forward instead of being caught at the trigger sear when the trigger was allowed to go forward during reset. As the title states, the AR was doubling. A poster a while back had the same or similar issue; and improper disconnector spring installation or a burr on the disconnector were guesses as to that problem, but the OP never followed up with their resolution.
Due to the hazardous operation, I have only dry fired the gun. I did do some FCG component swapping with known good parts and after determining that the disconnector did not appear to be the problem, the hammer appears to be the culprit in my case. Comparing all of the good parts to the problem parts with the unaided eye, I can't see any difference. I have sent an email to the vendor but in the mean time, any thoughts? TIA |
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Sounds like a function check saved you possible "embarrassment" at the range. I don't think enough people do a function check when they assemble an AR, let alone when they finish cleaning and reassembling it.
If you've tracked the problem down to a flaky hammer, (i.e. swapping parts around gives you a functional trigger group only when a different hammer is installed, and that hammer does odd things when it's installed in another lower), then I think you're done. Hammers are cheap, though they require some precision in manufacturing. I hope the vendor gets back with you quickly. |
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Thanks for your thoughts.
The parts are unmodified. I had the chance to do a close up inspection this afternoon. The hammer is bad. The notch that the disconnector latches into is cut wrong and lets go of the disconnector too soon. The disconnector lets go of the hammer before the trigger locks in. As a prior poster said, always do a complete weapon check before you go hot. Not legal or medical advice, MHO, YMMV, etc. |
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