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So I finished my AR build about 2 months ago, but never got to go shoot it. This weekend it finally happened and I shot it. My setup is an Armalite Lower with DPMS Lower Parts Kit, this Del-Ton 16" M4 Chrome Lined Barrel Assembly, 2 of these Magpul PMAG Polymer 30 Round Magazines, and a DPMS Carrying Handle. I bought 500 rounds of .223 at a gun show, not cheap stuff, but not expensive either. I can’t remember the brand, it was from some company in Maryland I think.

Anyway…The first magazine of ammunition fed well, I was shooting slowly and taking time in-between shots to adjust the iron sights. However, the next mag of 30 jammed about 12 rounds into it (shooting these rounds a bit quicker than the last). The spent brass didn’t eject and the bolt started to carry a new round up the feed ramp. So I pulled the charging handle back and it didn’t eject, so I had to lock the bolt back, drop the mag, and shake those suckers loose. Then I inserted the mag, released the bolt and fired a round, and it happened all over again. So I try once more without success. My remedy was to switch mags. That didn’t help, it still jammed with either magazine. So I took the AR apart and sprayed some G96 triple action lube on the bolt assembly and in the upper. This solved the problem temporarily, the next few spent casings that failed to eject, did eject when I pulled the charging handle back. This happened a few times in a row. Then everything seemed to be okay. From then on it only jammed once every 25 or so rounds.

I have done some research and it seems as though my initial problem might be poor lubrication and the gun being dirty (I didn’t clean it after I assembled it, just wiped it all over with some oil and kept it slick). So tonight I cleaned the heck out of that thing. But I also read that it might be due to a gas leak. What do you guys think? Does this scenario sound like a gas leak? What else might it be? (FYI: the bolt does lock back after the last round ejects)

I didn’t intentionally take any pics of the FTEs but a few were caught on camera, and I have included them below.

I know I am a n00b so any advise would be greatly appreciated. Here are a couple of my newb questions too: Should I put any gun grease on the bolt or in the upper, or will G96 work ok for lubrication (and if so, is Tetra Gun Grease good grease to use)? and if the bolt is closed and I insert a magazine should the magazine catch and stay in (I ask this because it didn’t stay in on my AR if the bolt was closed, I had to lock the bolt back before the mag would catch)?

Sorry for the long post…





 

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Check your carrier key to see if it is loose. I believe your problem is a symptom of a loose carrier key. If it is loose, tighten it and stake it best you can.

Also, what type of ammo were you using? That could be a factor too, although it sounds more like a gas problem.
 

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what weight buffer is in it.

check the gas key, is it tight?

check the 3 gas rings on the bolt itself, are they staggered?
 

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Clean, lube, and upgrade your extractor with this :cool:

BCM SOPMOD Bolt Upgrade/Rebuild Kit



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You really think that could be the problem? I am not as experienced with this stuff as you, but it doesn't appear that he is using come crappy ammo that is sticking in the chamber. However, I do agree that the upgraded extractor tension does help shoot any ammo.
 

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Discussion Starter #6
Thanks for the quick reply guys... I will have to do some research to find out where those things are on my gun. haha, yea i'm that new to these beautiful rifles. and i'm not sure about the buffer, you are talking about the buffer spring right?
 

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Were you shooting in that first picture? Your mag looks like it is touching the bottom, and I've heard that if there is pressure pushing up on the mag, then you may have feeding/extraction issues? Just a thought...:confused:
 

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doesn't mean squat if they are.
it can mean no-go if they arent staggered.

also your chamber might be tight. no reason a standard extractor spring and bumper shouldnt be able to clear a spent casing.

Find someone in your area with a chamber reamer and make sure it is in spec.

and get some factory ammo to make sure that the stuff you are shooting isnt just garbage.
 

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Do you think the actually stay staggered 100% of the time? :wink:

AR15.COM :: Forums :: if bolt gas rings align...



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its called due diligence. rule out all possible factors. Is it a LIKELY factor, no. is it a POSSIBLE factor? One in a list of other factors that could be causing malfunction? possibly.

by the by, quoting arfcom is about as good as quoting mickey mouse. there isnt a thing that 99.99% of the people there could teach me (or probably you for that matter) about AR's at this point.

Truth be told, it is most likely a magazine, or chamber issue. But again, due diligence is needed, especially for a build cobbled together from suspect parts (dpms, dti).
 

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Why are dmps and dti parts suspect? I've had great luck with both of the companies you've named, and so have many others...
 

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Why are dmps and dti parts suspect? I've had great luck with both of the companies you've named, and so have many others...
both companies have been known to make "not to spec" parts. and when you start mixing and matching, you get tolerance stacking. You are generally better off to go with a 100% dti gun, or 100% dpms gun, etc.....the heinz 57 guns tend to have the most issues.
 

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Sounds like a gas problem to me. Check the gas key make sure it's on tight and the gas key screws are staked. Check Front sight base, and gas tube. Make sure the gas tube is fitting well into the gas key.
 

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The bolt couldnt be in the carrier backwards could it?

I know you can physically put it in incorrect. But I do not know the results there after
 

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The bolt couldnt be in the carrier backwards could it?

I know you can physically put it in incorrect. But I do not know the results there after

+1--check to make sure the extractor is on the right side...also the ejector can be installed backwards, might want to check that too.

--John
 
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