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Centerfire Rifles - Semiautomatic or Gas Operated Centerfire rifles, carbines and other gas operated rifles.

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  #1  
Old 05-17-2010, 10:09 AM
vormav vormav is offline
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Default need help: ar-15 hammer not being cocked between shots

I finished building my ar-15, and right now i'm having a problem of the hammer not being cocked between shots. I load the magazine, and pull the charging handle, the first round will fire, the empty case will eject and a new round will be loaded, but then when I pull the trigger it wont fire, I pull back on the charging handle again and eject the second round, and the third round will then fire normally, and eject the empty casing. I'm not sure where to begin looking, whether it would be a problem in the upper receiver, or with the lower receiver, or if it could be a problem with the buffer tube somewhere.


I have a S&W stripped lower receiver
RRA lower parts kit
A2 style stock, can't remember the brand
m16 A1 complete upper half I bought from somebody here off calguns

I'm at work right now but I can take pictures tonight if needed.
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Old 05-17-2010, 10:17 AM
natedogg1777 natedogg1777 is offline
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The same thing happened with mine when I built it some 4+ years ago. Unfortunately, its been long enough to where I can't remember exactly what it was. All I remember is that I put something in backwards...probably a spring or something like that in the trigger assembly.

Is there a good amount of tension when you pull the hammer back manually? If not, you probably did the same thing I did.

Good luck!
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  #3  
Old 05-17-2010, 10:18 AM
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Sounds like your BCG isn't cycling (imagine like a bolt gun). But I'm not sure what can be causing that. Hopefully someone will have something for you.
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Old 05-17-2010, 10:19 AM
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http://www.calguns.net/calgunforum/s...ad.php?t=32797

try taking a look at your springs..
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Old 05-17-2010, 10:21 AM
Cyclepath Cyclepath is offline
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I assume you assembled your lpk correctly? Double check it with a reliable source or assembly manual. What kind of ammunition are you using? Check the carrier key to see if it is on tight and check the gas tube for leaks. You may need to remove the tube and inspect for excessive carbon around the port. Of course, make sure the bcg is clean and well lubed.
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Old 05-17-2010, 10:21 AM
BONECUTTER BONECUTTER is offline
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Sounds like your missing/or have installed backwarks the disconnector spring.

Now you are getting hammer follow. Its just not following fast/hard enough to fire like an auto would.
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  #7  
Old 05-17-2010, 10:27 AM
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A few things to check:

1. Disassemble your bolt carrier group, and make sure the three gas rings on the bolt itself have gaps that aren't lined up. If the gaps are all in a row, then too much gas will get past the bolt and it won't cycle all the way back.

2. Pull out your hammer and trigger. Triple check (find a diagram) to make sure that your trigger spring is in correctly, and that the disconnector is sitting in your trigger correctly, and that the little spring under the disconnector hasn't gone missing or gotten pinched/tweaked.

3. Check out your buffer tube with the spring and buffer removed... check for foreign matter or dents that could impeded the buffer going in and out all the way. Take a look in there with a flash light, and if it looks good to go, make sure you can drop the buffer without the spring in it and that it will go all the way down and out again (you'll have to shake it out) without getting stuck. Sometimes the roll pin on the buffer can start to come out and bind up on the inside of the tube.

4. If everything checks out perfectly up to this point, the only other things I can think of would be unlikely... they would include a: a blockage in the gas key on the bolt carrier, b: the gas tube installed upside down (yes, you can do this), or c: ****ty ammo.

I'd say that if 1, 2, and 3 check out fine, take it to a shop and have them give it the once over.
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  #8  
Old 05-17-2010, 10:32 AM
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Here's a function check for a bad/backwards disconnector:

With the rifle UNLOADED and NO MAGAZINE:

1. Charge the rifle
2. Pull the trigger with your left hand, and keep the trigger held down, don't let it go.
3. While holding down the trigger, charge it again with the other hand.
4. Slowly release the trigger. If it goes "CLUNK", it's good to go, if it really doesn't make a sound, then the hammer didn't get captured by the disconnector and followed the BCG forward.

A way to hold it to is put it on a bench pointing at the sky (resting on the butt), and hold the grip with your left hand, with your thumb on the trigger.

That "clunk" is the disconnector letting go of the hammer, and it being caught by the trigger, ready to fire again. Pulling the trigger again should make the hammer fall.
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Old 05-17-2010, 10:54 AM
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As an aside... I just did a check on YouTube to see if anyone has made a standard Marine Corps LTI (limited technical inspection) for the M16 variant rifles. There's nothing there... so perhaps I'll film one and put it up. An LTI is what you do to a rifle before each time it goes out to the range to make sure it's good to go, and will catch most problems.
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Old 05-17-2010, 12:55 PM
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Thanks for the replies, and that link with the pictures in it. I used the guide I found from here, calguns, for my LPK assembly, and the ammo I was using was a mix of remington, PMC, and ammo bros reloads. I'll check all the springs again tonight, and try Jason's function check
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Old 05-17-2010, 12:59 PM
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Either your rifle is short stroking like UserM4 said or as a couple people have pointed out the fire control group was installed incorrectly. If the fire control group was installed incorrectly that is an easy fix, just pop it out and put it back together again. Search "AR15 function check", you should do that after building an AR lower. If it short stroking that could be a difficult one to answer, do it reliably hold the bolt back after firing the last round in the magazine? If it does reliably hold the bolt back it probably isn't short stroking.

Quote:
Originally Posted by Jason_2111 View Post
1. Disassemble your bolt carrier group, and make sure the three gas rings on the bolt itself have gaps that aren't lined up. If the gaps are all in a row, then too much gas will get past the bolt and it won't cycle all the way back.
That is a myth. The AR will run with one gas ring, it has been done. Besides it is obvious that the gas rings are going to rotate themselves while firing.
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Old 05-17-2010, 1:30 PM
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I had the same issue and it was either my hammer or disconnector. I just replaced both and my problem went away.

Here are the parts:

Disconnector: http://riflegear.com/p-291-disconnector.aspx
Hammer: http://riflegear.com/p-303-hammer.aspx

That should fix it. My lower parts kit was a stag by the way.
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  #13  
Old 05-18-2010, 9:44 AM
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Quote:
Originally Posted by Josh3239 View Post
That is a myth. The AR will run with one gas ring, it has been done. Besides it is obvious that the gas rings are going to rotate themselves while firing.
Though it may run on one, it's a really bad idea.
Another problem with a lined up gap is the chance that as the rings shift around, one can trap itself behind another and seize up. Yes, I've had to repair this error a few dozen times.

These are failures that may happen... which is what I should have been more clear about.

The Marine Corps small arms school at Aberdeen Maryland doesn't teach myths. Though it's not a certain failure, it's taught to every Marine (and certainly every Soldier as well) as what you should do at the operator level in boot camp. It may be a little over-cautious... but certainly not a myth.
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The inevitable explosion gets closer and closer, coming in little steps, but closer every day.
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Old 05-18-2010, 11:41 AM
vormav vormav is offline
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Quote:
Originally Posted by Jason_2111 View Post
Here's a function check for a bad/backwards disconnector:

With the rifle UNLOADED and NO MAGAZINE:

1. Charge the rifle
2. Pull the trigger with your left hand, and keep the trigger held down, don't let it go.
3. While holding down the trigger, charge it again with the other hand.
4. Slowly release the trigger. If it goes "CLUNK", it's good to go, if it really doesn't make a sound, then the hammer didn't get captured by the disconnector and followed the BCG forward.

A way to hold it to is put it on a bench pointing at the sky (resting on the butt), and hold the grip with your left hand, with your thumb on the trigger.

That "clunk" is the disconnector letting go of the hammer, and it being caught by the trigger, ready to fire again. Pulling the trigger again should make the hammer fall.

after taking the hammer and trigger group out of my AR, i double checked the springs and they are in correctly according to all the guides I read, but when I tried your function test, I didn't hear the clunk.

I was noticing in the link with all the pictures of the various internal pieces someone posted here, the spring between the disconnector and the trigger was protruding up a little bit, but when I installed mine again, it was pushed all the way down by the disconnector. Could this be the cause of my problem? is that spring supposed to stick up a little bit, or should it be fully inside the trigger assembly?
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Old 05-18-2010, 11:52 AM
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Quote:
Originally Posted by vormav View Post
after taking the hammer and trigger group out of my AR, i double checked the springs and they are in correctly according to all the guides I read, but when I tried your function test, I didn't hear the clunk.

I was noticing in the link with all the pictures of the various internal pieces someone posted here, the spring between the disconnector and the trigger was protruding up a little bit, but when I installed mine again, it was pushed all the way down by the disconnector. Could this be the cause of my problem? is that spring supposed to stick up a little bit, or should it be fully inside the trigger assembly?
Yup, as I said before your disconnector spring is in wrong or you are using the wrong one. Lots of people put the bolt catch buffer spring in there by accident.
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Old 05-18-2010, 12:33 PM
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Quote:
Originally Posted by BONECUTTER View Post
Sounds like your missing/or have installed backwarks the disconnector spring.
This.

The most common problem is installing the disconnector spring upside down.
The LARGE end of the spring gets pushed down into the trigger which is much more difficult than putting the small end into the trigger.
That's why people do it backwards.
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Last edited by ar15barrels; 05-18-2010 at 12:35 PM..
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Old 05-18-2010, 1:51 PM
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Quote:
Originally Posted by ar15barrels View Post
This.

The most common problem is installing the disconnector spring upside down.
The LARGE end of the spring gets pushed down into the trigger which is much more difficult than putting the small end into the trigger.
That's why people do it backwards.
^^ That.
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Quote:
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The inevitable explosion gets closer and closer, coming in little steps, but closer every day.
I say: "Let's do it and get it over with."
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