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Posted: 10/23/2016 11:23:21 AM EDT
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I built my first AR. Anderson kit was used.
I test fired one round and it went great. Then I loaded two in the magazine and the first round fired great and the second round was cycled into the barrel with no problems but the trigger didn't reset. I repeated this process for three other tests with the same result. From what I know and understand about the springs and trigger assembly it all looks good. I even put in two dummy rounds to test things. Thinking it may be a gas block issue not pushing things back the bolt carrier back far enough I manually pulled back the charging handle only far enough to load the next round. The trigger was set and ready to fire that next round. What may be my problem? Have any of you seen this issue before. Thanks for your help |
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Likely the disconnector spring installed upside down or missing. The trigger is in fact cocking again, but releasing as you let off the trigger, where it strikes the back of the bolt carrier before it's back into battery, losing all its energy. Final condition is hammer down on a live round in the chamber.
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Before getting too deep, have you cleaned the gun correctly (including scrubbing the chamber with a chamber brush and CLP), and the upper receiver bearing areas have been correctly CLP lubed?
When you load on a single round into the mag, insert the mag, charge the round and fire it with the empty mag still in the mag well, does the bolt lock back on the bolt catch (catch in front of the bolt face, and not just catching the bottom of the carrier instead)? If yes, and yes, to the above, then the problem is not a cycling problem, but a other problem instead. So now lets get deep into the checks and fixes, 
And note that the disco spring gets installed fat side down into the trigger tail slot, with the smaller side upwards towards the bottom of the trigger tail. The fat side can be a bitch to installed, and somethings you have to use a set of pliers to squeeze the spring to get the coil in place. Next is the hammer spring, and it easy to install it the wrong way on the hammer before you install the hammer in the receiver, 
Next the fun one, and if you can flick the safety to safe then back to fire and you get the trigger pull to release the hammer on the second shot, then either a bur that is not allowing the hammer to come off the disco at trigger release, a bur that is not allowing the trigger to rotate on the cleanly (you did remember to lube all the parts, including pins before you installed the FCG), or you are using an after market pistol grip/forget to install the grip bolt head washer and now the tip of the grip bolt is protruding up into the lower receiver void under the trigger tail, and not allowing the tail of the trigger to come all the way back down. This covers the areas on the FCG to check for burs before you install it, 
And as for the grip bolt, with the FCG parts out to check them for burs, install just the grip with bolt and head washer to make sure that the tip of the bolt is not protruding into the lower receiver. If it is, either add another bolt head washer, or just shorten the bolt instead. About the only thing not covered above is either the bolt not fully locking up to allow the hammer to be released, or the disco out of timing instead. Note, the bolt is fully locked up with the front face of the carrier is tight against the back face of the barrel extension, and before the rig is even shot, it needs to be given a full cleaning (including scrubbing the chamber with a chamber brush and CLP, then once cleaned, the upper bearing areas need to be given a CLP lubing. On bolt lock up problem (rifle is passing the full stoke test by locking the bolt back on the single loaded and fired test), pull the bolt off the carrier and with just the carrier with Key, dry fit it into the upper receiver. The sides of the key should not be binding on the side of the receiver key slot, and when the front of the carrier gets about a inch from touching the face of the barrel extension, the gas tube should enter the key cleanly. If the gas tube needs to be re-indexed since it not entering the carrier key cleanly, then tweak the gas tube over the center of the barrel to align it with the key. On the bolt, if you are running a D fender or O ring around around the extractor spring, remove it and run the rig without the added O ring. The O ring can add to much tension on a new build and since the extractor has to spring open and climb over the bolt rim at loading, too much tension on the extractor can keep the bolt from fulling locking up correctly. Lastly, double check the disco timing free gap. With the trigger untouched, cock the hammer back to get the hammer back sear as close to the disco sear as you can. The free gap between the two should be in the .001" to .003" range (about that of a hair), and not larger instead. The free gap should in in this range instead. 
If the free gap is too big to start with, pull the disco and take a look at the front bottom of it where is seats against the top front of the trigger. The discos are stamp cut most of the time, and the front bottom of it can have off peen that you may have to file off to get the bottom edge of it flush instead. Disco that the front bottom surfaces over peen needs to be flushed to get the ideal free gap isntead, 
If a simple clean up of the bottom edge does not bring the free gap back to check, then the disco may need to be re-timed instead. http://www.ar15.com/forums/t_3_66/656984_AR_pistol_problem.html |
| I've troubleshot a trigger that wouldn't reset automatically after a round was fired. It would, however, reset if the safety selector was switched to safe. The rifle would than fire once again after being switched back to fire but not reset automatically once again. Turns out that the trigger guard was bent slightly upward so that the end of the trigger would wedge itself against the trigger guard with enough tension to keep it from resetting. Swapped the bent trigger guard for a spare unit and all functioned as it should... |
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