Took my mystery box build out to the range for the first time and it failed to eject. Thought it was a gas issue and readjusted the gas tube. Went back to the range and the first mag cycled well, no failures. Every mag after that failed to feed or double fed. What is causing this and what can be done? I have tried 3 different types of mags, and even the mag that cycled fine the first time did not work properly again.
New AR-15 Build Won't Cycle
- Thread starter jbroomie
- Start date
"readjusted the gas tube"?? is it a safe assumption you mean the gas block, do you mean the gas key? what was wrong with it? how did you fix it? My gas tube doesn't have any adjustments. It's either pinned in, or it's not. but either way, fixing a gas issue won't be the first thing I'd look at for a failure to eject issue (that's typically a bolt , chamber or ammo issue)
Are the mag's known good mags or are they new? how many rounds were loaded in the mags? are there any known good parts in the firearm? Failure to feed could be under gassed, double feeding rounds could be a mag issue. You are a little light on details for me to be able to help.
Start simple.
Try a known good mag, put 1 round in it, chamber this 1 round, fire the round, and identify the the round extract? did the round eject? did the action lock open. repeat 5-10 times, if the firearm consistently locks open, you are not under gassed.
Did it extract the rounds? no? see if someone has a bolt you can borrow/test with, try different ammo.
Did it eject the rounds? if it's extracting the rounds, but leaving them lying there in the action it's not ejecting see if someone has a bolt you can borrow/test with.
In what direction did the round get ejected (2 oclock, 4 oclock, 6 oclock)?
If those shots worked consistently and reliably, then up it from there, don't try to make your ar "run" if it can't "walk"
take that same known good mag, load 2 rounds in it (load one from it), fire that round, does it still extract and eject that round, do a press check, did the 2nd round get stripped off and chambered? does it fire that second round? does the action hold open still? increase the load out to 3, 4, then 5 rounds.
there should be a pattern of what works, and what doesn't work.
Are the mag's known good mags or are they new? how many rounds were loaded in the mags? are there any known good parts in the firearm? Failure to feed could be under gassed, double feeding rounds could be a mag issue. You are a little light on details for me to be able to help.
Start simple.
Try a known good mag, put 1 round in it, chamber this 1 round, fire the round, and identify the the round extract? did the round eject? did the action lock open. repeat 5-10 times, if the firearm consistently locks open, you are not under gassed.
Did it extract the rounds? no? see if someone has a bolt you can borrow/test with, try different ammo.
Did it eject the rounds? if it's extracting the rounds, but leaving them lying there in the action it's not ejecting see if someone has a bolt you can borrow/test with.
In what direction did the round get ejected (2 oclock, 4 oclock, 6 oclock)?
If those shots worked consistently and reliably, then up it from there, don't try to make your ar "run" if it can't "walk"
take that same known good mag, load 2 rounds in it (load one from it), fire that round, does it still extract and eject that round, do a press check, did the 2nd round get stripped off and chambered? does it fire that second round? does the action hold open still? increase the load out to 3, 4, then 5 rounds.
there should be a pattern of what works, and what doesn't work.
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pygmalion2020
Regular
- Location
- Eastern Ontario
I had an issue like this before and it caused by me installing the bolt backwards in the boltcarrier. The ejector was on the wall of the upper side not on the ejection port side.
jmichelin84
CGN Ultra frequent flyer
- Location
- Big Land, nL
What length is your gas and buffer system cuz they're supposed to be the same and as the last poster said check your bolt head in your bolt carrier group also check make sure you have the gas hole binder in the gas Block and Barrel
The gas block seemed to be misaligned and was not allowing gas to travel down the gas tube. The bcg was not cycling the first trip to the range. I realigned the gas block and returned to the range. This time the first mag cycled 10 rounds, properly ejecting and feeding all of the rounds. Following this, the bcg didn't seem to travel back far enough to pick up the next round. When the mag was emptied the bcg would catch partially back. The double feeds seemed to be user error. The rounds were ejecting at around four, some were catching the brass deflector as there are a few dings on it.
It was quite cold outside and this was only the second time the rifle had been fired, is this part of the so called "break in" period?
Gunnerlove
CGN Ultra frequent flyer
- Location
- Vancouver Island
Any decent bolt would be staked to prevent this from happening.
pygmalion2020
Regular
- Location
- Eastern Ontario
Gotta love those older NEA's eh?
How did you do that, they only go in one way.
This sounds like the gas issue isn't fixed or the GB moved? if the BCG isn't traveling back far enough, then it sounds like its not enough gas. Is the GB pinned? or does it use allen screws? Good quality ammo should "seat the gas rings". Other than that, good luck, feeding issues are usually 99% of the time mags? unless there is something obvious with the feed ramps?
Cameron SS
CGN Ultra frequent flyer
- Location
- Ground Zero
When you get a double feed, is it two live rounds, or a live round and a fired case?
Given that you think the gas block was misaligned, lets focus on that, and forget about the mags for a second.
Sounds to me like you are under gassed. Alignment could be an issue. Or the gas block could simply be loose. Or the barrel profile could be too skinny for the gas block. is there any evidence of gas escaping the block where it sits on the barrel?
Or the block or barrel could have too small a gas hole.
I would not expect this to be a break in issue.
Heres some things that may or may not make your problem better or worse. When you detect change, you are honing in on the problem.
Check/Replace gas rings.
Check/replace the gas tube
Check/replace the gas block. Inspect for gas hole diameter.
Sea Monkey
Regular
- Location
- South Coast of Upper Canukistan
I had a similar issue with a new build and started troubleshooting with the most difficult fixes I could think of, as well - the gas block. Eventually I checked the bcg and found that the gas tube thingummy on top was loose and wouldn’t catch enough gas to reliably cycle. Check those two Allan screws on top of the bcg?
