HELP Weird Cycling Issues 10.5"

[steyrman13]

See if you all can help me figure this out. I don't know why I am wasting my time with it other than to help a friend of my friend. Real help would be direct him to get a better upper. This is a 10.5" Facebook Gunsmith upper! Oh yay!

I don't know who the manufacturer of any of the upper parts are. 10.5" barrel with gas port measuring .071 with my digital caliper and .076 on the label on harbor freight drill set so take that for what it's worth both ways.

It will not lock back on empty mag or feed the next round. Sometimes the bolt will sit on top of the round it is trying to feed.
I have tried different lowers two of which were known good. 10 different mags all which work in other rifles. Different buffers. Carbine, h and h2. Different buffer springs, different BCGs. All of the lowers and his BCG work in other ARs and my 10.3 DD on his lower. The only parts that don't work is his upper with barrel gas block and tube.

I pulled the cheap rail off and found the clamp on gas block to have one broken screw and the other as tight as allowed and it would still slip off. I thought I had found the issue. So I put a new gas block on and still have the same issue except it will lock back sometimes now.

Any ideas?

[ColtSeavers]

Try a new gas tube or cleaning the gas tube? All I got off the top of my head if everything else works when swapped into known good uppers.

ETA: Which buffer is currently in it that it is now sometimes locking back?

[Auto-X Fil]

You can test by sticking a piece of hose on the end of the tube that sticks into the gas key and blowing. Compare to your DD. I bet it feels plugged up somehow.

Is the gas tube protruding into the upper the correct amount?

[steyrman13]

Try a new gas tube or cleaning the gas tube? All I got off the top of my head if everything else works when swapped into known good uppers.

ETA: Which buffer is currently in it that it is now sometimes locking back?

I have not tried a new gas tube yet, although pulling it off and comparing to one off of a currently working BCM, they both fir the gas key of his and one of my BCG the same(which doesn't mean that it is a true fit).
This was going to be my next test.

It seemed to work the same sporadically with h2 or carbine. That's the weird part.

[steyrman13]

You can test by sticking a piece of hose on the end of the tube that sticks into the gas key and blowing. Compare to your DD. I bet it feels plugged up somehow.

Is the gas tube protruding into the upper the correct amount?

I'll try this tomorrow too.

[steyrman13]

I forgot to mention, it acts the same with hot 5.56 as with weaker 223.

[bfoosh006]

Deleted

[MistWolf]

Is it leaving a spent case in the receiver? If so, it's most likely an extraction problem.

If not, either the gas block is leaking, or the port in the barrel does not line up with the port in the gas block. Also check for s blocked gas tube

[rabbitcop]

What length gas system is it? Pistol or carbine?


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[steyrman13]

Is it leaving a spent case in the receiver? If so, it's most likely an extraction problem.

If not, either the gas block is leaking, or the port in the barrel does not line up with the port in the gas block. Also check for s blocked gas tube

I believe it has to be the tube.
No, the shells are extracted, it just fails to pick up the next round.
The barrel could be out of spec as even the new BCM gas block was looser than I like when installing it, but not loose enough to wiggle. The gas hole is lining up as the ring around the gas port from the gas block shows it to be perfectly centered. I am going to check to make sure the gas tube isn't the issue.

THIS IS WHY I RECOMMEND QUALITY BRANDS TO MY FRIENDS. I WISH I WOULD HAVE KNOWN HIM BEFORE HE PURCHASED THIS CRAP TO PREVENT ALL THIS IN THE FIRST PLACE.

I'll report back as soon as I get a chance to take it back to the range for more testing.

[steyrman13]

What length gas system is it? Pistol or carbine?


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Carbine length. It is definitely related to the upper, barrel, gas block, or tube. His BCG worked fine on my rifles. And his lower worked fine on my DD upper even with his BCG in my DD upper.

[rabbitcop]

Is it made of metal? Was it made in China? [emoji1][emoji1][emoji1][emoji1][emoji1][emoji1][emoji12][emoji12][emoji12][emoji12]

I'd scrap it and tell him to buy something from a reputable company. I've seen some nice 10" uppers for $300-400 recently


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[steyrman13]

Is it made of metal? Was it made in China? [emoji1][emoji1][emoji1][emoji1][emoji1][emoji1][emoji12][emoji12][emoji12][emoji12]

I'd scrap it and tell him to buy something from a reputable company. I've seen some nice 10" uppers for $300-400 recently


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I am rarely one to throw the towel in, I like a challenge, but I also hate dealing with junk when you can spend a tiny amount more and never have to worry about this crap lol.

[rabbitcop]

Godspeed on your endeavor


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[steyrman13]

Come to think of it, it might be the same guy on one of the local Facebook groups that built this beauty I fixed in post 24 of this thread....Gunsmithing Hall of Shame Thread
https://www.m4carbine.net/showthread.php?t=162898

I should just start posting in every thread they list for sell a service charge or free trade in for a quality upper deal!

[JoshNC]

Don't throw good money after bad. That upper sounds like a total turd. I would just let it be a lesson to your friend of a friend why he shouldn't buy garbage.

[titsonritz]

Come to think of it, it might be the same guy on one of the local Facebook groups that built this beauty I fixed in post 24 of this thread....Gunsmithing Hall of Shame Thread
https://www.m4carbine.net/showthread.php?t=162898

I should just start posting in every thread they list for sell a service charge or free trade in for a quality upper deal!
That is the California compliant model, yeah?

[steyrman13]

I have it running now. I am going to recommend he sells it and let's me build him a better upper though.

I tried another gas block and tube. And it is running now.

The first replacement block with his tube I could plug the gas port in the block where it meets the barrel and blow through the gas tube and have leakage around the tube blowing back in my face although very slightly. I think his barrel is slightly undersized at the gas block section as all blocks I tried still slid on with no resistance mixed with slight leak around the gas tube where it interfaces with the gas block must have allowed enough bleed off to cause the under-gassed symptoms. I used some locktite to help "bed" the gas block and the BCM gas block I ended up using fit the best. I'm sure it was probably leaking under the gas block and around the gas tube with the first replacement I tried.

Thanks for the ideas to look at. I figured I would get some suggestions that I was overlooking.

[rabbitcop]

Good job and thanks for the update. I would suggest that since you've pretty much replaced everything else, I'd have him buy a barrel. Radical Firearms has some nice barrels for around $100. I love their stuff


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[marine0811]

Thanks for this post, it may help those with similar issues in the future.

[ColtSeavers]

Good job and thanks for the update. I would suggest that since you've pretty much replaced everything else, I'd have him buy a barrel. Radical Firearms has some nice barrels for around $100. I love their stuff

Rabbitcop, if you've been lucky this far, I am very glad for you, but please do some research on the problems with Radical Firearms if you've not already, they are a dice roll.

OP, do not use Radical Firearms anything as you run a much higher risk of being right back in the same situation you are in now or worse. Radical firearms has a lot really bad Quality Control issues and is not considered a top tier trustworthy manufacturer/vendor because of this.

Glad you were able to finally fix his mess.

[rabbitcop]

Thanks for the tip. I'll be weary next time


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[rabbitcop]

Been lucky with RF so far but all I have is a 300blk pistol upper from them. I wouldn't trust 6.8x43 to anyone but Harrison.


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[steyrman13]

Good job and thanks for the update. I would suggest that since you've pretty much replaced everything else, I'd have him buy a barrel. Radical Firearms has some nice barrels for around $100. I love their stuff


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I am just going to suggest selling the complete upper. I don't know the quality of the parts in the upper either as the ejection port cover hinge pin and c clip were broke off as well!

What a mess lol!
I have a BCM BFH 11.5" I might hook him up with if he will listen to my advice.