First AR build...cycling issues. UPDATE 8/4/17 PROBLEM SOLVED

Sorry guys, work has been busy and I've been only able to get out on weekends.

I changed out the carbine buffer spring, thinking that it was causing the issue. It did not cure the problem.

The issue is consistent. With one round in the mag. it fires the round, but the bolt will not come back far enough to lock back or pick up the next round. ejection is consistent in the 3-3:30 range. Brass looks clean.

Under gassed is certainly where I'm leaning. However, I have also ordered a rifle buffer (I'm running a 20-inch barrel) and rifle butt stock. I didn't like the looks of the carbine stock on the longer gun. Dropping in a rifle buffer, flat wire spring (Tubbs) and longer A2 stock might change things up.

I've examined the bolt and bolt carrier and see no wear keeping it from moving smoothly. The BC passes the gas ring test.

Dave at Black Rifle Works has been helpful and I may send the bolt back to have a qualified person examine it looking for burrs or blockages.

Instead of throwing more money at this, I'll be trading out parts with a working AR. If I trade out lowers and the problem persists, I can eliminate the lower as being an issue. Same with the bolt and upper. This should pinpoint my issue.

I promise to update the post until its fixed...it just may be weekly.
 
Good luck on your quest. I had the same issue with a new 7.62X39 upper on a proven, actually three, lowers.

The Drill Fairy visited and gave me a bigger port and a BTE adjustable block had me running. It only took one trip to the desert to diagnose that one!! LOL

Greg
 
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So I finally decided to take my upper down and examine the gas block assembly and gas port. I blew out the port and didn't see any obstructions. I also plugged the gas block port and blew air through the gas tube. No leaks.

The barrel port and the gas block port looked to be well aligned. I was about to put it back together when I noticed the gas marks inside of the gas block. It looks like the gas is bleeding off between the gas block and the barrel (see top photo). There also seems to be a gassing mark on the top of the barrel around the port (see bottom photo).

My question: does this look like a normal gas pattern for a rifle that has maybe 20 rounds through the tube? It appears to me that too much gas is bleeding off between the gas block and the barrel likely causing my cycling issue. If this appears excessive (I don't know) how would I go about fixing this? I guess I could send the upper back (I purchased it assembled from CBC).

As always, thanks for the comments and suggestions.
 
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Greg, seeing the gas markings on the two photos, do you think too much gas is being lost between the gas block and the barrel? Looking at your photo, I don't see any gas markings outside the concentric circle around the gas port. I don't see that on my bas block.
 
Yep I think there is way to much leakage there. My picture is about as good as it gets. I'd probably put s different block on it like Jor Bob's adjustable. If no go s bigger port drill or maybe it's time to call calf rope and send it bavk.

I admit all mine are customs from Ritch over the past six years but I rarely get to trouble shoot. The 7.62 was the first one that really was problematic. I rework extractors and rjectors but in over 40 uppers only under-gassing resulted in these symptoms. Leakage id more than likely the culprit.

Greg
 
Gas leakage would now be my guess, given your picture. I had a cheap 4 rail gas block, have a very similar soot pattern, and it also was failing to lock back, and in some cases, even eject spent cases completely. I called the vendor, and they admitted having more than one unhappy customer with this gas block, and offered a refund or replacement. I took the refund. I had a bunch of old A2 sight/gas blocks in the spare parts pile, and replaced the suspect gas block, and the rifle ran like a champ. I was replacing the free float forearm with a Matrix Keymod, so I got a Wilson Combat Adjustable GB, and the gun runs well, now.

You should try a different gas block, if you haven't already. Unless your barrel isn't machined correctly under the gas block, I am betting a well machined GB will fix your issue.

Squeeze
 
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Squeeze and Greg, thanks for the input. When I removed the GB and saw the gas pattern, I suspected it was the issue. I have contacted the vendor and we'll see what happens.

As was mentioned, this is my first build and diagnosing this issue has taught me a lot about how these rifles work...or don't work.

Thanks again for all the input and helping me out with suggestions of the problem.

I'll keep everyone posted on what happens from here.
 
UPDATE:

I contacted CBC Industries last night explaining the issue. I didn't send the photos, just explained the problem. They stated they don't ever have issues with the 20-inch upper and it had to be one of two things; gas block/gas tube almost alignment or a faulty gas block not fitting the barrel and bleeding off gas.

They instructed me to take it apart and take a look. I sent him the photos above and they agreed it is the issue. I shouldn't have gas marks like what was pictured.

They gave me the option of sending me out a gas block assembly so I could replace it or I could send it back and they could take care of it. They also said that they would test fire the upper after the repair to make sure things are done in order. I'll be sendIng it back.

I understand issues happen, but what defines a company is how they handle themselves when issues pop up. This was my first build, so my first upper purchase. CBC was priced right and the delivery quick. The fact that I have to send it back doesn't bother me at all. I'm hoping they can fix the GB quickly and return it to me.

It'll go out today.
 
Originally Posted By: SwitchUPDATE:

I contacted CBC Industries last night explaining the issue. I didn't send the photos, just explained the problem. They stated they don't ever have issues with the 20-inch upper and it had to be one of two things; gas block/gas tube almost alignment or a faulty gas block not fitting the barrel and bleeding off gas.

They instructed me to take it apart and take a look. I sent him the photos above and they agreed it is the issue. I shouldn't have gas marks like what was pictured.

They gave me the option of sending me out a gas block assembly so I could replace it or I could send it back and they could take care of it. They also said that they would test fire the upper after the repair to make sure things are done in order. I'll be sendIng it back.

I understand issues happen, but what defines a company is how they handle themselves when issues pop up. This was my first build, so my first upper purchase. CBC was priced right and the delivery quick. The fact that I have to send it back doesn't bother me at all. I'm hoping they can fix the GB quickly and return it to me.

It'll go out today.


That's pretty good attitude to have. Lots of guys just blow a gasket and rant and rave about issues. No one in manufacturing is perfect and dealing up front with you is kudos to them. I mean have any of us, I know it's not manly, had to rewash a dish we didn't get right the first time? It's just some soap, water and a scrub brush and we screw that up!

We see guys get their panties in a wad because XXX isn't right and my god I'll be without my new toy for two weeks. OMG!!! Really? They need to get a life.

I bet that less than 5% of the guys on here can't walk over to a safe of closet and pull out something perfectly acceptable for the task at hand. [beeep] some of us could walk to the safe over three dozen times and still be reaching in!!

Keep us posted and let us know how the replacement runs.

Greg
 
Greg, not the way I'm wired. For me, some things aren't worth getting upset about. What's broke can be fixed.

I also give vendors the benefit of the doubt and one chance. CBC has already demonstrated they are more than willing to make things right. I read over 100 ratings of CBC before I purchased and almost all were pleased with the product and the customer service. You're always going to have a few that they'll never make happy, but most were pleased with the company...good enough for me.

CBC also stated that they'd test fire the upper and make sure things run good. To me, that's as good as it gets.
 
UPDATE:

As mentioned the upper was sent back to CBC Industries. They mentioned that the repair should be quick and that they would test fire the upper. The upper was in their shop for a little over a day and on its way back to me. That's about as prompt as it gets.

The FedEx package arrived yesterday. The packing slip stated that the unit had been repaired (new gas block assembly) and test fired eight times.

I wasted no time in installing the upper and I headed out this morning to test fire the rifle.

I first ran the single round test in the mag…after the round was fired, the bolt remained back and the chamber open. That is the first time this rifle has ever done that. I ran three different magazines through the AR, along with five different types of ammo in .223 and 556 (I settled on a .223 Wylde barrel allowing the use of both .223 and 556 ammo)…the rifle performed flawlessly.

I slow fired the rifle and rapid fired it as well, all went smoothly.

No jams, no stove piping, no issues of any sort.

I then started shooting for accuracy as was beyond impressed with the preliminary groupings of this set up. Despite the early issues, I am very happy with the build and the results.

CBC Inc. is an awesome company and handled my problems quickly and efficiently. If I ever decide to build another rifle, I'll be buying from them.

Thanks to all who offered advice on this problem and a big hats off to all that pinpointed the problem (under gassed) quickly.
I'll post up a photo of the beast later today.


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My shooting buddy
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Such a great feeling of relief when they shoot to expectations. Way to hang in there. I know it can be frustrating but I am glad you got your gun running.
 
Originally Posted By: SwitchUPDATE:

As mentioned the upper was sent back to CBC Industries. They mentioned that the repair should be quick and that they would test fire the upper. The upper was in their shop for a little over a day and on its way back to me. That's about as prompt as it gets.

The FedEx package arrived yesterday. The packing slip stated that the unit had been repaired (new gas block assembly) and test fired eight times.

I wasted no time in installing the upper and I headed out this morning to test fire the rifle.

I first ran the single round test in the mag…after the round was fired, the bolt remained back and the chamber open. That is the first time this rifle has ever done that. I ran three different magazines through the AR, along with five different types of ammo in .223 and 556 (I settled on a .223 Wylde barrel allowing the use of both .223 and 556 ammo)…the rifle performed flawlessly.

I slow fired the rifle and rapid fired it as well, all went smoothly.

No jams, no stove piping, no issues of any sort.

I then started shooting for accuracy as was beyond impressed with the preliminary groupings of this set up. Despite the early issues, I am very happy with the build and the results.

CBC Inc. is an awesome company and handled my problems quickly and efficiently. If I ever decide to build another rifle, I'll be buying from them.

Thanks to all who offered advice on this problem and a big hats off to all that pinpointed the problem (under gassed) quickly.
I'll post up a photo of the beast later today.


1697.jpg

1698.jpg


My shooting buddy
1699.jpg


I just got a 10.5 pistol kit from them in .223 and it’s also undergassed. Gas block appears to be properly aligned but the carbine spring they sent me is 2” longer than the other ones I have and is noticeably stiffer, thinking it might be that.
 
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