What about his rifle gas system with a carbine buffer system

 

Shouldn't matter. Lots of people runs such a combo. I've ran carbine uppers on rifle lowers, and rifle uppers on carbine lowers with no issues

The tube doesn't look terrible, unless it is pressfit there is always going to be some gas leaking there. Fix the rings and try again.

This is my first DI gun so my knowledge is minimal but I read that the aligned gas rings will make a problem worse but not cause the problem in the first place. Again from what I've read

I'd ordinarily agree, but you clearly have a problem, so you solve it by working your way through the obvious first.

 

Also, you should save your brass and look at it for any issues, are the cases showing any rim damage? are they showing pressure signs? Scratches and dents?

Marty, 

 

From the pic, it looks like you might be running your bolt/bcg dry?

 

If that is the case, take you bolt and lube the gas rings and cam pin generously with oil.  Next, put some grease on the bcg rails and a lil bit on the inside of the receiver where the bcg makes contact.  

 

Even hi tech coated bcgs need lube, despite the hype.

 

If lube isn't the issue, I'll reply with a quicky gas system check up.

 

 

Everything was lubed, BCG, inside of upper, buffer tube, but you are right, the bolt did appear dry up pretty quickly, I used MPRO-7 LPX which is what I use on everything thing else, which grease should I be using?

 

I do have all the brass, at first glance it looked fine but I will check again more closely tonight. I did notice some minor scratches on the of the brass nothing on the rim.

 

But unfortunately I won't be able to get back to the range for another few weeks.

Everything was lubed, BCG, inside of upper, buffer tube, but you are right, the bolt did appear dry up pretty quickly, I used MPRO-7 LPX which is what I use on everything thing else, which grease should I be using?

 

I do have all the brass, at first glance it looked fine but I will check again more closely tonight. I did notice some minor scratches on the of the brass nothing on the rim.

 

But unfortunately I won't be able to get back to the range for another few weeks.

I still suspect you have a lube issue, based on the photo. ARs like to be run wet.

 

The other likely possibility is a gas issue, as many have mentioned. Here is my gas block/tube check:

 

Buy a 1 foot length on a small vacuum line from the auto parts store. Pull you bcg out of the upper. Attach the vacuum line to the end of the gas tube, where it normally goes into the gas key. Now, blow into the hose that is attached to the gas tube. You should easily be able to blow a steady stream of air. Next, plug both ends of the barrel with a cloth rag. Blow into the tube again and see if it holds pressure and is much harder to blow into. At the same time, listen for air leaks around the gas block and gas tube connection to the block by dabbing a lil water at the seams. A tiny, tiny bit of leakage is ok.

 

If leakage seems to be ok, perhaps you have a gas block alignment issue. If so, take the block off. Use a pencil and straightedge and draw a long, straight line on the barrel, througn the gas port. Then, do the same on the gas block, up the front lip of the block. Those are your alignment marks. Reassemble and check airflow with the vacuum line again.

 

If that or lubing doesnt fix it, the only thing i can think of is garbage ammo.

 

I have seen 1 odd, related issue with a bent upper receiver/ejection port issue caused by improper clamping techniques, but that shouldnt be the case, if you used an upper clamping block, to assemble. That can be checked by seeing if the bcg slides freely, without binding half way.

I checked the brass, i don't see any signs of overpressuser.  But i did notice some horizontal line, is it getting stuck in the chamber? 

Ok, so I ran a leak test today. I basically blocked off the breach using a spent casing and the BCG, I then put a straw in the muzzle and taped it and the MB with electric tape. I then blew compressed air into the straw at about 110psi while pouring oil on gas tube at the GB and as you can see from the video, it is leaking profusely. I am thinking that the combination of this leak and the aligned gas rings caused my problem. Looks like it's time to order a better quality gas tube, any suggestions?

 

https://youtu.be/NDiIYTuNvPE

Ok, so I ran a leak test today. I basically blocked off the breach using a spent casing and the BCG, I then put a straw in the muzzle and taped it and the MB with electric tape. I then blew compressed air into the straw at about 110psi while pouring oil on gas tube at the GB and as you can see from the video, it is leaking profusely. I am thinking that the combination of this leak and the aligned gas rings caused my problem. Looks like it's time to order a better quality gas tube, any suggestions?

 

https://youtu.be/NDiIYTuNvPE

Don't get fixated on the rings being aligned. I have seen ARs run on two or even one ring with no issues. The leak is the primary concern and ascertaining why it is leaking should be your focus.

 

It could also be the block, so keep in mind that swapping the tube may not solve the issue. I am

Going through the same issue right now. After swapping the gas tube and making sure the gas block was properly aligned, I am still having an issue being undergassed. Going to swap the gas block next week. If that doesn't do it, I need to look at the barrel and make sure the gas port is sized correctly or there isn't a deformity or irregularity on the barrel causing the gas block to not seal properly.

But what about the leak, is that normal?

I have never tested a gas block/gas tube that way, but I can't imagine that is normal gas leakage.

That looks like a pretty bad leak. It could be the gas tube, it could be the gas block. Buy the cheaper one first (tube) and try again.

 

In my experience, when they match well it is a pain in the ass to get the gas tube in the gas block and I have to hammer on the back (front?) of the gas block with a wood block to get them all the way mated.

Yeah, the gas tube did go in pretty easy. Just ordered another one, we will see what happens.  Thanks guys for all your help, I really appreciate it.

I hope the new gas tube fixes it. If it's the block then I will have to cut it off and get a 2 piece. There is no way in hell that I am destroying that muzzle brake. Worse case scenario, anyone try a high-temp RTV or fire barrier caulk around the tube to block connection point?

The 2 piece isn't the worst option..I have a YHM 2 piece on mine and that effer works fine and won't budge no matter how much I try

 

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The RTV would be the worst option, if its even an option

Do you really want a glued together rifle??? 

The 2 piece isn't the worst option..I have a YHM 2 piece on mine and that effer works fine and won't budge no matter how much I try

 

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That's my next fix attempt. I'm going with this one with the Gas Tube already installed:

http://www.njgunforums.com/forum/index.php/topic/80663-jp-gas-block-jpgs9/?p=1027317#entry1027317

Well if the new tube does't fix it I'll be buying the 2 piece GB

This will be a little long winded but bear with me. I changed the gas tube and ran the same test, and it still leaked the same if not worse then the original. I figured 2 bad tubes from 2 different manufacturers, not likely. But at this point a new gas block is a last resort. Then after watching a few youtube videos I decided to try something. I put a spent case from my last range trip and slammed the bolt forward to make sure the extractor engages and tried to rack the CH, sure enough it was tight, it took a good hard yank to pull it back. Ok, the case is getting stuck in the chamber, so that I the reason for the short stroke I think. And yes I did clean the barrel out initially but not the chamber, my screw-up, lesson learned. So I cleaned the chamber really good and got back out to the range this morning.

 

The final outcome, had 1 FTE half way thru the second mag but after that over 300 rounds without another hiccup. It runs like a switch watch now. It is still under gassed, ejecting at 5 o'clock but it's cycling just fine. Hopefully the under gas problem goes away once the gas tube seals up.

 

As far as accuracy goes, take a look at the pictures at 100yds, with cheap 55gr PMC ammo and a weaver kaspa scope

 

I would say that's just about 0.5 MOA

 

And here is about 200 rds at 100 yds

 

 

Now, the Cryptic Coatings BCG after 300 rds

 

After a wipe down with a dry paper towel in front where the logo is

 

I would like to thank everyone for all your help. I would say this build is a success   

 

I also want to give a big thanks to Steve from Monmouth arms, he hooked me up last minute with the MB and pinned it over night for me before my first range trip.

Marty, I know you posted it but I can't find it:

 

What are the barrel specs? Make? Chamber?

 

What ammo were you shooting?

 

Thanks.

The barrel is a Ballistic Advantage 223 Wylde 20" rifle length, here is the link.

http://ballisticadvantage.com/20-inch-223-wylde-dmr-rifle-length-ss-premium-barrel.html

 

The ammo was cheap 55gr FMJ-BT PMC Bronze.