I have an AR with strange issue

[Fallbackpuppet]

My daughters rifle worked fine for the last three years firing several thousand rounds without issue and recently began acting up. It will fire the first round without issue and will feed the second but then click and won't fire. So for my first test I swapped the upper including BCG with my rifle my rifle functioned normally and hers did the same thing with my upper as with hers. At that point I replaced the trigger group all of it including pins (as it seemed the most likely suspect) however the issue persists. I then removed the trigger group and put both her old group and the new group in my lower. My rifle preformed normally after that I reassembled my rifle and put the new trigger group back in her rifle. The problem persists. Anyone have any ideas?

 

[OK Corgi Rancher]

Have you tried more than one type of ammo? That's usually the first thing I do with a problem...try a few different types. At least you can quickly eliminate that as the culprit. You can also do a thorough cleaning of the chamber and BCG on her rifle...make sure all the hardened carbon residue is removed. Is her bolt going all the way into battery when it chambers a round? Make sure it's not stopping short.

 

[dlbleak]

Weak buffer spring?

 

[Fallbackpuppet]

Weak buffer spring?

I can replace it, but it cycles without issue so I didn't consider that. You insert the mag, chamber a round and it fires fine. The action cycles and feeds the next round without issue, but when you squeeze the trigger you get a click rathe than a bang. I suppose that could happen if the bolt isn't returned fully to battery so I will replace the spring (it does appear to be correctly locking up however). I hope some micro misalignment due to the spring getting weak is the problem.

 

[O4L]

You're saying "click and it won't fire". Is the trigger resetting and it is actually a click with no bang?

If not maybe it's low power ammo or something dirty in the gas system. Gas rings bad maybe.

 

[SPDguns]

Is the hammer spring installed correctly?

 

[Fallbackpuppet]

You're saying "click and it won't fire". Is the trigger resetting and it is actually a click with no bang?

If not maybe it's low power ammo or something dirty in the gas system. Gas rings bad maybe.

I cleaned it really well and the upper works fine on my lower with the same ammo. I am reasonably sure it is an issue in the lower.

 

[O4L]

Just thinking out loud here...If the trigger is resetting and releasing but not firing the round it could be that the trigger pin holes have become enlarged causing things to become misaligned.

 

[GlockPride]

Is the hammer spring installed correctly?

Yep, yep, because you know, I’d never, ever put a critical spring in wrong….well, maybe, but I ain’t admitting here in a public gun forum….no way…

 

[Fallbackpuppet]

Just thinking out loud here...If the trigger is resetting and releasing but not firing the round it could be that the trigger pin holes have become enlarged causing things to become misaligned.

That is possible. I have never heard of it before and if not sure how I would check it (unless nothing else works and then I have to replace the lower)