So this AR is brand new, so I expected it to take a break-in period before running, but let me explain.

The issue is this, on some rounds, after firing, the spent case will eject but a new one won't feed. Another issue was that the bolt was not closing all the way when returning. Also, it would return, but stay out of battery by 1/2 inch or so with no round stripped from the mag. at one point I believe I had a double feed. All times, the empty case ejected. Also, the bolt held back on the last round.

So here are the possibilities:

New: Only had a chance to get 100 rounds downrange before we had to leave, and I stupidly left lube back at the house. Shoot some more and bring the lube, as it was tight.

Norgon mag release: could pressing either up or down on the mag, causing the issues of why its not holding open on last round??

Open the gas port: I have one of the $169 DD barrels, and some have reported needing to open the gas port by .003 of an inch in order to get it feeding reliably.

So, any opinions are welcome, I can provide more info if needed

Gun was built,

DD barrel
BCM BCG and CH
Mega upper
VLOTR gas block
carbine buffer and spring
UBR buffer tube(with UBR of course)


ETA: Took off the rail tonight and unscrewed the gas block.

Here is a pic of the gas port on the barrel



Doesn't look quite even.


And here is something else I've noticed, the beginning of the gas tube right behind the GB has carbon burns "leaking" out of it. At least I'm pretty sure its that.



does this mean my gas tube is out of spec?

ETA: like anyone cares, but ill update anyway : Well it came back from ADCO and I just got around to shooting it last week. Damn it ran great! all rounds fed and ejected, though I had one stuck case which I would attribute to switching between brass and steel from mag to mag.

was the BCG lubed well?  ARs don't require break-in to function properly.

ETA: what ammo were you shooting?  If it was underpowered that could explain it.  Also, was or wasn't the BCG locking back after the last round?

When a round doesn't feed is it stripping one off the mag and jamming?, or not stripping one at all?

I'd try new ammo, and a new mag for starters. I don't think opening up the gas port will help with the feeding that you describe.

Some sounds like new gun crankiness, but try mags and ammo first.  

Sometimes the ammo would jam before chambering all the way, the ammo was Q131, and handloads that I have not had an issue with over 1,000 rounds in my other AR. The BCG was lubed, not dripping wet, but pretty well.

Mags were a 4 different 30 round pmag and a 20 round pmag

Well, damn. I was sure you were running wolf 55. gr and 1 pmag. I had one mag that I just couldn't get to feed right with my BCM middy, same type of malfunction you were describing.

Hows the fit once your home, does it chamber fine when it's empty?

How often?

[/quote]


Hows the fit once your home, does it chamber fine when it's empty?

How often?[/quote]


rounds slide in and out of the chamber just fine, what do you mean does it chamber fine when it's empty?

At first it was doing it every round. After the first mag and a half, I got 3 rounds, by the 3 mag I think I got 12-15 rounds before it malfunctioned, than back to every round.

Is the gas block aligned correctly?

I'm going to take a wild guess on this one. Did you mount the VLTOR gas block all the way against the shoulder of the barrel? If so, maybe it is covering some of the gas port on the barrel. When I mounted my VLTOR gas block, I used a round hadguard cap that i cut a notch out of so I could space the gas block away from the shoulder. If I didn't do this, and mounted it all the way to the shoulder it would have put the gas port at the brink of being covered.

That's another thing I'm wondering. I aligned it by sight, lining up the threads for the screws to the dimples on the barrel. It seemed correct to me.

^^^ This. The vendor who helped me install my upper assembly used a hand guard cut in half in order to space the gas block from the shoulder correctly.

Load 1 round in a mag and fire.  If the bolt does not lock back, then perhaps it is undergassed.  You have a normal carbine buffer, so too heavy a buffer isn't the issue.  See above posts regarding gas block alignment.

Thanks, I will return to the range with a lot more lube and try that. If that doesn't work, I will check the gasport again.

Hoping that it fixes itself next time, taking a DD rail off is tedious with all that unscrewing to do

sounds like it is short stroking which is a gas problem... lubing the bolt carrier is a putting a bandaid on the problem.  check the gas port to see if it is lined up.

Took off the rail tonight and unscrewed the gas block.

Here is a pic of the gas port on the barrel



Doesn't look quite even.


And here is something else I've noticed, the beginning of the gas tube right behind the GB has carbon burns "leaking" out of it. At least I'm pretty sure its that.



does this mean my gas tube is out of spec?

That all looks normal actually.  Eventually, with enough carbon build up there will stop being leaks.  The marks around the gas port also show that the gas block was close enough... the entire port on the barrel is covered.










 

Like I said, some Q131 and reloads pretty close to max.

buffer and spring were as follows-for carbine gas tubes

http://dsgarms.com/ProductInfo/DSATCARB.aspx

http://dsgarms.com/ProductInfo/DSATCCARSPR.aspx

How well lubed was the gun?  Anything feel like it was dragging when you charged it?  How well does the gas tube fit into the carrier key?  Have you done a test of the bolt's gas rings?

It sure sounds like the thing is slightly under-gassed, but that would only be a valid diagnosis if all these other things (and probably more) were fully accounted for.

And here is something else I've noticed, the beginning of the gas tube right behind the GB has carbon burns "leaking" out of it. At least I'm pretty sure its that.

http://i155.photobucket.com/albums/s297/bigg089/IMG_0393.jpg

does this mean my gas tube is out of spec?[/quote]

Is this how your gas block is installed in the bottom picture?  I have the same block and there is a small gap(very small) between the shoulder and the gas block itself and works great.

I had a build with the DD barrel and the rounds would jam on charging 90% of the time.  Thought it was bolt and/or buffer spring, mags, etc... After trying to remedy these items I removed barrel and noted sharp burrs on feed ramp bolt slots (needed a magnifying glass to see.) It was literally jamming the bullet into the burred slot. Dremeled and polished and the problem went away.

Mark the shell casing with a line horizontal to the ejection port and charge, and then check for lines/gouges perpendicular to line (this will tell you if it is feed ramp or just lines from extraction as round drags horizontally on the right on extraction.)

Also, after this problem was corrected this is one of the most accurate barrels I have bought lately with close to MOA off the bench with 25.8 Gr. 748 and IMI 62 Gr. FMJSCBT.

Just my personal experience, and you will find similar problems with charging on the Troubleshooting section.

Is this how your gas block is installed in the bottom picture?  I have the same block and there is a small gap(very small) between the shoulder and the gas block itself and works great.[/quote]

No, the picture on the bottom is after I removed it from where I installed it.

From everything I can tell, you do not have a gas leak.  The tube looks normal, the port would indicate that your gas block is placed correctly, not to mention, if you have a dimpled barrel, they basically self align since the screws and the dimple are tapered.

My guess is you got one of the DD barrels with a slightly undersized gas port.  Common problem with those barrels, so its the most likely source of the problem.  You are using a good BCG, good ammo, but your rifle is firing as if its under-gassed.  Everything else seems to check out just fine so I'd start there.  The symptoms you are describing indicate it being under-gassed, and based on the evidence and the components used, the barrel is the most likely culprit.

Trip back to DD might be in order.

so long that everything is lined up, you'll probably need to drill out the gas hole just a little more.

Thanks for the replies, I will see in the next couple days what I can do about measuring the gas port.

What kind of tool would I be looking at for doing this?

Ideally, pin gauges.  Otherwise just use a caliper and eyeball it.  But pin guages will give you the best, most accurate reading.

I can get the calipers to go from .058 to .061 or so, so I will look i to some pin gauges.

Tag!

I've got an almost exactly similar issue with a Bushy of mine.  I posted in the troubleshooting forum.

Dano there suggested looking for the carrier dragging on the hammer as one possible thought.  I'm still running my issue down but I'm leaning toward a gas issue as I see no other visual evidence(I haven't removed by gas block/FSB yet.
I'm gonna change BCGs for troubleshooting.

So, old thread, I know

I've shipped my upper to the gentlemen at ADCO. This will give me a chance to review their work, but from the emails alone I have been very satisfied

I will post a updates on it as they happen

I'm interested in what ADCO finds if anything.

For and update, I finally removed my BCG and replaced it with the stock BCG and the thing ran fine.  I had been running the Young NM BCG.  Those are heavier than the one that came with the gun.  So either the stock BCG is light enough it's masking a gas issue or there's something about the YNM BCG that that particular gun doesn't like.  I did install the YNM BCG in a new upper I just built and so far it's been running perfect.  For me however when I first installed the YNM BCG into the gun that was giving me issues lately, it didn't have these issues.  That makes me think it's something else that is causing the troubles.

Well they shipped my upper today. I'm curious to see if they leave a note as to what was wrong. Will find out next week

when it fires, where does the brass land, that will tell you if you are over or under gassed.  Also, is your extracter straight?  Correct spring and inserts?

nevermind

update in OP

I was following!

This pics do not show anymore.

As for the "leaking" around the gas block, I think this is kinda normal until you shoot it enough to eventually get it carboned up enough so it finally carbon block all the leaks.  At least that was I have read on Arfcom.

What did ADCO say they did or find on the barrel?

No letters or anything so I'm not sure what they did. I could rehost the pics if I can find them, but it just showed an alligned gasport ring on the gasport