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6/8/2014 6:09:54 PM EDT
I just built an AR and the first 25rds shot were flawless. Then I had issues with rounds not being fed. After every round, it would eject, but the next round wouldn't chamber. Tried multiple mags, still continued to do the same thing. What are your opinions? I'm thinking it may be an issue with the buffer/spring, or maybe a lubrication issue. Thanks in advance.
6/8/2014 6:22:14 PM EDT
[#1]
Check the gas system.
6/8/2014 6:32:05 PM EDT
[#2]
Is the front sight base pinned or srewed on?...check gas key tightness its short stroking sounds like a definate gas issue.
6/8/2014 6:45:48 PM EDT
[#3]
It sounds like it's short stroking. Like others suggested, check the screws on your gas key on the BCG and gas block, or  pins on FSB.  If all that is tight, maybe try a lighter buffer
6/8/2014 7:24:03 PM EDT
[#4]
Yup, short stroking.  Gas block is tight??  If set screw re check it. In the case of my BCM 20" it did exactly the same thing.  But I was running wolf gold and AE223.   With 556 it was fine. I drilled out the gas hole two sizes and it runs like a champ on anything now.  

If there are no gas leaks and you don't want go drill you can run a Wolff springs reduced power recoil spring. I'm running one on my SPR so it will run cheap ammo and always lock the bolt back ( wouldn't until I did this... At least not consistently .. ).   Definitely worth the $15 did the trick

Also make sure the gas tube isn't  slightly angled putting excess pressure on the BCG as this can also slow the BCG down and make it short stroke
6/8/2014 7:31:53 PM EDT
[#5]
Gas system seems to be in check. Not loose at all. What frustrates me is that it ran fine. Sighted in the scope and fired multiple rounds rapid fire. Then it just started acting up.
6/8/2014 7:36:37 PM EDT
[#6]
Quote History
Quoted:
Gas system seems to be in check. Not loose at all.
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Any idea on gas hole size? What brand barrel?  My spikes carbine barrel I used was only a .062 and I had to open it up to .070 to make it run cheaper ammo ( always ran it but wouldn't lock the BCG back.. )

Strangely enough the only barrel I've left alone is my 14.5" middy BCM, eats shit for breakfast and loves it.
6/8/2014 8:38:32 PM EDT
[#7]
Did you remove the gas block to see where the carbon mark is?

Is this a low profile GB or FSB?

Barrel make?

Is GB up against the shoulder?

Give us the specs on the rifle so we can help you better.
6/8/2014 10:39:17 PM EDT
[#8]
Its a 14.5" Spikes lightweight barrel with a lopro gas block.
6/8/2014 11:36:32 PM EDT
[#9]
Quote History
Quoted:
Its a 14.5" Spikes lightweight barrel with a lopro gas block.
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BCG? Buffer?


6/9/2014 2:00:56 AM EDT
[#10]
Basic buffer, Spikes BCG.
6/9/2014 2:56:31 AM EDT
[#11]
Quote History
Quoted:
Basic buffer, Spikes BCG.
View Quote


What ammo are you using?  I'd pick up a box of 556 and see how it runs. If it runs fine on 556 but chokes on cheaper plinking ammo and your sure there are no gas leaks you may have to try the reduced power recoil spring or open up the gas port.  Or shoot more expensive ammo
6/9/2014 3:33:14 AM EDT
[#12]
I was using 55gr PMC 223 brass and 55gr American Eagle AR223 brass.
6/9/2014 5:05:09 AM EDT
[#13]
Its a gas problem, did you put the gas block on correctly? like leave a space for the front handguard cap.



take a mag w/ 1 round only, shoot it, does the mag catch engage, if not, its a gas problem.



Since its happened after heating up, all my money is on the gas block or a bad gas key on the bcg, there really is no where else it can "leak"
6/9/2014 5:39:32 AM EDT
[#14]
on my spikes 14.5 lw I had to go from a spikes buffer to a plain old carbine problem solved for me
6/9/2014 6:31:21 AM EDT
[#15]
Quote History
Quoted:
Its a gas problem, did you put the gas block on correctly? like leave a space for the front handguard cap.

take a mag w/ 1 round only, shoot it, does the mag catch engage, if not, its a gas problem.

Since its happened after heating up, all my money is on the gas block or a bad gas key on the bcg, there really is no where else it can "leak"
View Quote


This. Check for loose gas key, and did you leave the space between block and shoulder where a HG cap would be? 0.032" IIRC. If you know anyone with a borescope you can look "up" the gas hole from inside and verify alignment. HTH
6/9/2014 7:53:33 AM EDT
[#16]
Quote History
Quoted:
Gas system seems to be in check. Not loose at all. What frustrates me is that it ran fine. Sighted in the scope and fired multiple rounds rapid fire. Then it just started acting up.
View Quote



My guess is a lubrication issue. ARs are engineered to run wet. If you are running it dry, you will have issues.
6/9/2014 11:51:01 AM EDT
[#17]
Loose gas block screws causing block to shift and misalign with port after getting hot the first time, is my bet. Did you use a thredlocker on the screws? Check gas block out good, bet its loose.
6/9/2014 7:40:45 PM EDT
[#18]
Quote History
Quoted:
Basic buffer, Spikes BCG.
View Quote


What buffer? Carbine, H, H2??

Also what spring? Standard spring or a heavier one?
6/9/2014 8:47:50 PM EDT
[#19]
Gas block was on tight. It was the first thing I checked. It is a carbine buffer tube. Not sure what kind of spring it is, I bought it off of ebay a while back. It may be a while before I can really check your theories. I'm leaving for vacation this weekend.
6/9/2014 11:28:34 PM EDT
[#20]
Quote History
Quoted:
Gas block was on tight. It was the first thing I checked. It is a carbine buffer tube. Not sure what kind of spring it is, I bought it off of ebay a while back. It may be a while before I can really check your theories. I'm leaving for vacation this weekend.
View Quote


I wouldn't trust anything from ebay but that's me.

Just because the GB is tight does not mean it is lined up correctly. Like I said earlier, remove the GB and makes sure the carbon buildup mark is over the gas port of your barrel.
6/10/2014 1:14:04 AM EDT
[#21]
Quote History
Quoted:



My guess is a lubrication issue. ARs are engineered to run wet. If you are running it dry, you will have issues.
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View All Quotes
Quote History
Quoted:
Quoted:
Gas system seems to be in check. Not loose at all. What frustrates me is that it ran fine. Sighted in the scope and fired multiple rounds rapid fire. Then it just started acting up.



My guess is a lubrication issue. ARs are engineered to run wet. If you are running it dry, you will have issues.


THIS.... Especially on a new AR it needs to be wet till broken in.... Hell it always needs to be wet as far as I'm concerned. As easy as a remedy this is to check I'd start here before over thinking things....
6/10/2014 5:16:41 AM EDT
[#22]
Topic Moved
6/10/2014 5:29:42 PM EDT
[#23]
Its just a spring. Its not like it was a complete ebay build. And yes, the gas block was lined up correctly. This isn't my first, or even my 2nd build. But it is the first one I have had issues with.
6/10/2014 5:31:16 PM EDT
[#24]
I'm thinking and hoping it was a lubrication issue.
6/10/2014 6:37:07 PM EDT
[#25]
While there are many possibilities in my experience most of the time on a new build’s first time out it is lack of or improper lubrication.
Even with a generous lube job mine (new builds) generally want more lube around 60 rounds and will then run out past 200.
Bad mags run a distant second followed by other issues.
6/10/2014 6:51:08 PM EDT
[#26]
If it is a lubrication issue it would have to be almost dry.  I've ran mine wet and unbelievably dry just to see and they actually all ran fine fairly dry.


Lube, shoot and then move on. But before anything I'd see if it runs 556 ok
6/10/2014 10:42:11 PM EDT
[#27]
I tried multiple mags. Same thing each time. I am going to test the lubrication hypothesis as soon as I can.
6/11/2014 5:12:58 PM EDT
[#28]
The gas ring alignment thing is just a myth, right?  Have you looked at the gas rings on your bolt?
6/12/2014 7:13:01 AM EDT
[#29]
With a 14.5” barrel gas ring alignment is not likely to be a problem.
Given the number of people on the board who do think it is a myth it would be humorous if it was the problem.
6/13/2014 6:57:10 AM EDT
[#30]
Quote History
Quoted:
With a 14.5” barrel gas ring alignment is not likely to be a problem.
Given the number of people on the board who do think it is a myth it would be humorous if it was the problem.
View Quote


I know, I just figured it would be worth looking at in case it was something more than an alignment issue with the rings.  Maybe one or more are damaged, who knows.  Yes, I know some people have ran a rifle with even only one ring too...
6/13/2014 10:12:35 AM EDT
[#31]
I had a rifle that for sure did not like three rings lined up.
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