AR-15 Trigger Won't Reset

[SKILCZ]

Was shooting a friend's AR-15 that would fire the first round in the mag and chamber the second round, but the trigger would not reset. It is specific to the lower as it repeated with different uppers.

What are potential causes of this? To me, it seems to be a trigger reset issue since the BCG is cycling and feeding the next round. It's a QMS trigger on a lower with a PSA LPK.

 

[ClickClickD'oh]

By trigger not resetting, do you mean the trigger stays to the rear and won't travel forward, or does it travel forward, but pulling it again does nothing?

The first case is probably a improperly installed trigger spring. The second case is probably the disconnector not catching the hammer. Bad juju if the second.

 

[dogmush]

Did the hammer follow?

Look at the disconector and it's spring.

 

[SKILCZ]

Is there a way to test these things w/o firing or being at the range?

ETA: Found this post and did what it says:

Take the upper off. Try to reset the trigger by hand, first with your finger OFF the trigger. The trigger should catch the hammer at the sear.

Now you want to release the hammer. *DO NOT LET THE HAMMER DROP ON THE OPEN RECEIVER.* Keep your off hand thumb in front of the hammer, between the hammer and the reveiver. Pull the trigger and release the hammer.

Now HOLD THE TRIGGER DOWN and push the hammer down.It should catch on the disengagement hook. Then release the trigger. The hammer should then catch on the sear.

Let us know which of these tests fail, and we can help you figure out what to do next.

When I do the last (bolded) part releasing the trigger, the hammer seems stuck on what I presume is the disengagement hook and takes some finagling (seems like pushing the hammer down further is what works) to get it to reset to the sear.

 

[MachIVshooter]

When I do the last (bolded) part releasing the trigger, the hammer seems stuck on what I presume is the disengagement hook and takes some finagling (seems like pushing the hammer down further is what works) to get it to reset to the sear.

The disconnector (or secondary sear).

There's either a problem with the engagement surface of the disconnector and/or hammer, or the trigger spring is not strong enough to overcome it.

Is the trigger spring installed correctly?

This is the same issue I have right now with my 1/2 scale AR project, and it is because the trigger spring I made by straightening and re-profiling a coil spring simply does not have sufficient power.

 

[Walkalong]

Check all the parts, and make sure there is no debris, such as a primer, in the works. Clean and re-assemble. Safety check it before firing.

 

[cactus02]

Saw this same problem on a new gun. the parkerising was so rough the trigger spring would not reset the trigger. Oil on it( it was shipped dry) and thirty rounds latter it was functioning normally.

 

[ZGunner]

Try reversing the hammer spring (so it has more tension). I did this on my most recent lower build and fixed the problem immediately.

 

[MachIVshooter]

Try reversing the hammer spring (so it has more tension). I did this on my most recent lower build and fixed the problem immediately.

 

[dprice3844444]

http://www.ar15.com/archive/topic.html?b=3&f=66&t=300427 here is some pictures of trigger spring installation.

http://www.ar15.com/content/guides/assembly/lower/

 

[SKILCZ]

Thanks, all. I will take it apart, see if I can figure out what the issue is, and post back.

 

[Blade First]

When all else fails, your quick-time friend is a valid youtube vid or ar15.com tutorial. Your firearm is unsafe but the problem is likely quite clear and easily fixed. Once you have eliminated the obvious...a broken part...then proceed with deliberation. Under no circumstances should you fire the weapon until all is well.

Like others offering advice, I think it's highly likely that a part has been installed incorrectly. Fix it and then run through the multi-step function test until you are satisfied that selector and disconnector are performing correctly.

Please PM me if I can be of help...will be happy to give you my shop number.

Be safe...Alex

 

[srkavanagh6621]

I had this issue with a faulty safety during one of my builds, you may want to look at that too.

 

[Justin]

If it's an adjustable trigger it's possible for one of the adjustment screws to move to the point where it causes a dead trigger, or if it's been adjusted to have a very short take up, it's possible for the trigger to become worn causing inconsistent trigger pulls and hammer follows.

 

[Dr.Zubrato]

Check all the parts, and make sure there is no debris, such as a primer, in the works. Clean and re-assemble. Safety check it before firing.

This.
I've run guns so dirty chunks of carbon have gotten under the fire control group. Nothing worked until I stripped it down. The real weakness of the AR15 is the fire control group, IME.

 

[Warp]

The first thing I would do, definitely, would be as mentioned above...take the FCG (and selector while I'm at it probably) out of the lower, inspect everything closely, and carefully re-install following known-good instructions step by step.

If it's an adjustable trigger it's possible for one of the adjustment screws to move to the point where it causes a dead trigger, or if it's been adjusted to have a very short take up, it's possible for the trigger to become worn causing inconsistent trigger pulls and hammer follows.

I believe it has an ALG QMS, which is not adjustable.

Try reversing the hammer spring (so it has more tension). I did this on my most recent lower build and fixed the problem immediately.

...what?

Are you sure you didn't initially install the hammer spring incorrectly, and when you "reversed" it, you put it in the right way? It can take a small amount of work to get the hammer in and line the pin up properly since the hammer spring isn't exactly weak.

 

[RUDY850]

were the trigger comes threw the lower may need opened up a little.the trigger might be rubbing and not letting it reset.i have read others have had the same problem and that fixed it.

 

[ZGunner]

Are you sure you didn't initially install the hammer spring incorrectly, and when you "reversed" it, you put it in the right way? It can take a small amount of work to get the hammer in and line the pin up properly since the hammer spring isn't exactly weak.

I followed Larry Potterfield's directions on the MidwayUSA YouTube channel.

When initially installed it looked exactly like the linked picture in post 10.

Broke it down, flipped the spring, now it works...