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ukdkbr
05-30-2009, 12:55 PM
Me and my dad built an AR15 for him a little while ago. We took it to the range for the first time today and had some trouble that I hope you guys can help with.

It will fire the first round fine and eject the casing, then chamber the next round but it will not fire at all. He had to manually eject the round and then chamber another round, the next round would fire fine. Then we noticed that after the first successful round is fired and the next one is chambered when you pull the trigger nothing happens, BUT if you move the safety to "safe" then back to "fire" it will then fire that round, we tried this several times and every time we cycled the safety to safe then back to fire the round would fire. Any ideas?

This is a LRB lower with a RRA parts kit.

Cal-Irish
05-30-2009, 1:08 PM
Long shot and probably not the cause but check that the trigger pin isn't "walking" out of place.

Texas Boy
05-30-2009, 1:13 PM
Sounds like something isn't assembled correctly in your fire control group. Where are you located? Perhaps there is a Cal gunner near by who could take a look.

BTW - do you have any snap caps? You should be able to diagnose this problem at home with action proving rounds. Start with the lower and insure all the springs were properly installed and the pins are retained properly as Cal-Irish pointed out.

Hopi
05-30-2009, 1:19 PM
Me and my dad built an AR15 for him a little while ago. We took it to the range for the first time today and had some trouble that I hope you guys can help with.

It will fire the first round fine and eject the casing, then chamber the next round but it will not fire at all. He had to manually eject the round and then chamber another round, the next round would fire fine. Then we noticed that after the first successful round is fired and the next one is chambered when you pull the trigger nothing happens, BUT if you move the safety to "safe" then back to "fire" it will then fire that round, we tried this several times and every time we cycled the safety to safe then back to fire the round would fire. Any ideas?

This is a LRB lower with a RRA parts kit.

By nothing happens, do you mean that the trigger pulls but the firing pin doesn't strike, or, that when you pull the trigger, the trigger doesn't move?

ukdkbr
05-30-2009, 1:22 PM
By nothing happens, do you mean that the trigger pulls but the firing pin doesn't strike, or, that when you pull the trigger, the trigger doesn't move?

You know the weird thing was that it looks like there was a very light strike on the ejected rounds that did not fire. I will ask my dad what he felt since he was the one pulling the trigger. Maybe he'll sign up and chime in, he should be watching this thread :rolleyes:

FCinCA
05-30-2009, 1:22 PM
Did you install the LPK yourself? Check your hammer install and do a function test.

Hopi
05-30-2009, 1:27 PM
You know the weird thing was that it looks like there was a very light strike on the ejected rounds that did not fire. I will ask my dad what he felt since he was the one pulling the trigger. Maybe he'll sign up and chime in, he should be watching this thread :rolleyes:

I wonder if the bcg isn't lubed enough and subsequently isn't flying forward completely when it tries to chamber a new round?

ukdkbr
05-30-2009, 1:30 PM
I wonder if the bcg isn't lubed enough and subsequently isn't flying forward completely when it tries to chamber a new round?

You know that could be it, it seemed to me that it was pretty dry.

Additionally the very first round he fired would not eject the shell, it looks like the extractor ripped off the lip of the casing, we had to use a push rod to get the shell out. See the attached image

Arteel
05-30-2009, 1:30 PM
Funny, same thing was happening to me with my .22lr upper. I blamed it on the ammo though, but have not gotten a chance to take it back out to see if the problem still exists. Let us know if you get it figured out.

Jicko
05-30-2009, 1:31 PM
A potential problem - installed the disconnector the wrong way .... check the disconnector spring, make sure it is installed the right way....

Sounded like the cycling of the BCG is not cocking the hammer.... potentially, it is a "hammer follow", but in a "good way"... ie. not firing the next round (or else you would have a "machine gun"....)

DO NOT try to fire again until you have make sure that your FCG is installed correctly...

ukdkbr
05-30-2009, 1:32 PM
Did you install the LPK yourself? Check your hammer install and do a function test.

Yes we did install it by our selves, my first build went fine and it looked like it was all functioning correctly after we had everything installed.

ukdkbr
05-30-2009, 1:34 PM
A potential problem - installed the disconnector the wrong way .... check the disconnector spring, make sure it is installed the right way....

Sounded like the cycling of the BCG is not cocking the hammer.... potentially, it is a "hammer follow", but in a "good way"... ie. not firing the next round (or else you would have a "machine gun"....)

DO NOT try to fire again until you have make sure that your FCG is installed correctly...

Agreed, after we put the rifle away after we realized something was way off.

ukdkbr
05-30-2009, 1:39 PM
Quick question, the disconnector spring, one end is larger than the other which way should it go? I assymbled my 2nd lower at the same time as my dads and we went step by step and they should be identical, I'm looking at mine and the "wide" end of the spring is on top sitting against the disconnector, is this correct?

Edit: I think I just answered my own question, I was looking here: http://www.ar15.com/content/guides/assembly/lower/#hammer
It says "Install disconnector spring with the wider portion of spring down towards trigger and push until it locks in there". Oops.

Texas Boy
05-30-2009, 1:41 PM
You know that could be it, it seemed to me that it was pretty dry.

Additionally the very first round he fired would not eject the shell, it looks like the extractor ripped off the lip of the casing, we had to use a push rod to get the shell out. See the attached image

Check the chamber lugs carefully. I had a similar problem due to a small piece of brass that was preventing the bolt from closing properly. Sounds like your bolt might not be going fully into battery due to the debris.

If the rifle continues to tear brass then you might need to install a heavier buffer to slow the extraction. Is this a 16" barrel with a carbine gas system?

Jicko
05-30-2009, 1:42 PM
Quick question, the disconnector spring, one end is larger than the other which way should it go? I assymbled my 2nd lower at the same time as my dads and we went step by step and they should be identical, I'm looking at mine and the "wide" end of the spring is on top sitting against the disconnector, is this correct?

THAT is your problem. (A serious one.)

"Install disconnector spring with the wider portion of spring down towards trigger and push until it locks in there."
http://www.ar15.com/content/guides/assembly/lower/

Fortunately it didn't fire a continuous multiple rounds.

BTW, when shooting your DIY built AR for the first time, please try to put only 1 (or 2 rounds max) in the magazine until you are sure that it is functioning correctly.

Cal-Irish
05-30-2009, 1:44 PM
You are going to jail now.

ukdkbr
05-30-2009, 1:46 PM
Check the chamber lugs carefully. I had a similar problem due to a small piece of brass that was preventing the bolt from closing properly. Sounds like your bolt might not be going fully into battery due to the debris.

If the rifle continues to tear brass then you might need to install a heavier buffer to slow the extraction. Is this a 16" barrel with a carbine gas system?

Yes, 16" carbine. After it did this, we took the mag out and removed the bolt/carrier and inspected it and put it back in after we extracted the messed up shell. It didn't do it to any other rounds.

ukdkbr
05-30-2009, 1:48 PM
THAT is your problem. (A serious one.)

"Install disconnector spring with the wider portion of spring down towards trigger and push until it locks in there."
http://www.ar15.com/content/guides/assembly/lower/

Fortunately it didn't fire a continuous multiple rounds.

BTW, when shooting your DIY built AR for the first time, please try to put only 1 (or 2 rounds max) in the magazine until you are sure that it is functioning correctly.

He did test fire 1 round at his house (he can get away with firing off a round every once in a while there) it fired fine and ejected the casing, we thought we were good to go.

FeuerFrei
05-30-2009, 1:50 PM
Heavy re-lube might cure this. I built up an AR a year ago and it passed the function test but would do the same as you describe.
I drenched the BCG w/CLP and it ran all day without a hickup!
Always try the simple things first.

Jicko
05-30-2009, 1:52 PM
He did test fire 1 round at his house (he can get away with firing off a round every once in a while there) it fired fine and ejected the casing, we thought we were good to go.

Actually, whenever I do at range function test for rifles that is firing for the first time, I would load 1 round, and then I would remove the magazine. Fire that 1 round and holding the trigger without releasing it, and make sure that it cycle, and no hammer follow, and the that the disconnector is correctly catching the hammer. And lastly, when i release the trigger, that I will hear/feel the disconnector releasing, and the trigger sear catching the hammer.

Ruiner
05-30-2009, 2:14 PM
You know the weird thing was that it looks like there was a very light strike on the ejected rounds that did not fire. I will ask my dad what he felt since he was the one pulling the trigger. Maybe he'll sign up and chime in, he should be watching this thread :rolleyes:

The light strike on ejected rounds are normal. The AR has a floating firing pin so theres nothing stopping it from moving forward when the bolt closes.

Arteel
05-30-2009, 2:14 PM
I had the same problem and my disconnector spring was installed correctly. :shrug:

Texas Boy
05-30-2009, 2:35 PM
You can dry fire test the disconnector. With an empty chamber, no mag installed and NO ammunition in the area:


pull the charging handle back and release. Bolt should be forward and the hammer cocked.
Check that the selector moves from fire to safe. This confirms that the hammer is cocked.
Move the selector to fire, point the gun in a safe direction, and squeeze the trigger. DO NOT release the trigger but continue to keep pressure on the trigger.
While holding the trigger fully depressed, pull the charging handle completely back and release .
Slowly release pressure on the trigger. You should feel and hear a click as the dissconector releases and the sear catches.
Verify that the selector will now move from fire to safe. If it does not, then your hammer is forward and the disconnector did not catch the hammer.
Squeeze the trigger again to verify that the hammer will drop after cycling.


This check should be performed anytime you remove/install parts from your fire control group.

ukdkbr
05-30-2009, 2:47 PM
Thanks guys I think we've figured out what went wrong, we're going to disassemble and flip the disconnector spring, and see if that fixes our issue!