AR Build Problem

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Olympus

Olympus

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I finally got to shoot my SBR today and have my first problem with a build. The gun is 11" and carbine gas system. The gun fires, ejects, and loads a new road all just fine, but the trigger won't reset after that first shot. I can pull the bolt back about an inch and let it re chamber again and the gun will fire. But it has the same issue with the very next round.

I've never had a problem with a trigger not resetting after each shot. What do I need to be doing here?
 
i remember having one like that, if i recall the spring on the trigger itself "the one that lays on the receiver bottom" was incorrectly placed. not lifting it back up to engage the sear. be careful, hopefully someone else will chime in.
 
Never had that problem, but I agree it is a spring installed incorrectly. Guess I have been fortunate, having built 20 AR lowers.
 
Remove the trigger group, clean everything, put it back in (Double checking the spring positions/orientation), and see what happens.

If that doesn't help, you may have a mechanical problem with the trigger group.
 
I'll take a look at it tonight. It's brand new, so there's nothing there to clean. But I'll take the group out and reinstall it.
 
The gun fires, ejects, and loads a new road all just fine, but the trigger won't reset after that first shot. I can pull the bolt back about an inch and let it re chamber again and the gun will fire. But it has the same issue with the very next round.

I've never had a problem with a trigger not resetting after each shot. What do I need to be doing here?
Click to expand...

Sounds like the disconnector is not doing its job and the hammer is following the carrier back. When you pull it back an inch to reset it you likely (shouldn't with a live round anyway) don't have your finger pulling on the trigger, so the disconnector is not in the picture.

Remove the upper and see it everything is acting right, disconnector/reset wise.

What trigger are you using?
 
I can pull the bolt back about an inch and let it re chamber again and the gun will fire.
Click to expand...
Factory ammo or reloads? Pulling the bolt back 1" is not going to cock the hammer. If reloads, OAL to long or brass not sized correctly ?
 
I've had this problem, but only in a specific instance:

I had a Geissele HSNM trigger which uses a really strong hammer spring. I was trying to use a 22lr conversion and the blowback was not enough force to get the hammer to reset and the sear engage after firing a round. I played around with lighter hammer springs but never got it to work. This gun however worked just fine with .223/5.56 ammo.

I would suggest looking very closely at your hammer spring and sear springs.
 
I had the same problem with an ALG trigger group and a .22 upper. It worked just fine with everything else. Go figure.

To the OP. What LPK did you use?
 
Used an Anderson lpk. I've used them for at least 6 other build and never had a problem. Didn't get a chance to look it over last night, but I will tonight.
 
Olympus said:
Used an Anderson lpk. I've used them for at least 6 other build and never had a problem. Didn't get a chance to look it over last night, but I will tonight.
Click to expand...

Did it all work properly when you worked the hammer/trigger on the bare lower (stopping hammer from hitting receiver of course) and when you did a dry-fire function check of the complete rifle, prior to going live? Particularly when you pulled the trigger, held the trigger down, cycled the bolt, and then released/pulled the trigger...did it work?
 
I did dry fire the lower only and full rifle, just didn't hold the triggers back, cycle, then release and refire.
 
Just checked the trigger and everything is installed correctly and seems to be working right. I checked the dry fire functionality while holding the trigger back. I recycled the bolt and the hammer stayed cocked and the trigger reset and then fired correctly. I did this about 50 more times and it worked every time.

So I took the gun outside to test fire a few rounds. Now I have light primer strikes. On every single round. This is still factory ammo. What the heck?
 
I'm 99.9% certain my trigger group is installed correctly.
 
Swap the FCG for one that you know is good from another rifle/lower.

A picture of the FCG as it is installed, particularly the hammer spring, might ease some concerns people have about installation

Edit: I assume a person who is assembling their own rifle and references having used a specific part at least six times prior has an existing rifle/complete lower and/or a spare LPK/FCG.
 
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What did you change from post #1 to post #15?

Are you sure you are getting light strikes or is the carrier out of battery slightly and the hammer is not getting a good hit on the firing pin?

With a mil spec hammer it really doesn't take a lot of spring to set off a primer. Even if it only takes 3lb to push the hammer off the sear (further into the lower), with the inertia it builds getting to the firing pin is enough for reliable ignition (if everything else is right).

Who made the ammunition?
 
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I removed the bcg and trigger group and the reinstalled and test dry fired. When the trigger started resetting by dry fire, I thought I had the problem corrected so I went to test fire. Ammo is Tula and it's the same batch that I've shot thousands of rounds with in my other guns.
 
I removed the bcg and trigger group and the reinstalled and test dry fired. When the trigger started resetting by dry fire, I thought I had the problem corrected so I went to test fire. Ammo is Tula and it's the same batch that I've shot thousands of rounds in my other guns.
Click to expand...

I am still missing something, just removing and replacing the bolt carrier shouldn't change how the trigger is working.

How about taking one of your other guns that has always ran perfect and put the upper on your SBR lower.

If it runs, then install the SBR bolt and carrier in the same upper and see if it runs then.

If one of your other lowers is also an SBR install the upper on it with a known "good" BCG and see if it runs.

Process of elimination should take a fraction of time this thread has been running, to find the culprit.
 
jmorris said:
Process of elimination should take a fraction of time this thread has been running, to find the culprit.
Click to expand...
Precisely.

And with light strikes as a symptom I would jump straight to singling out the FCG, as I mentioned earlier.
 
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