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Discussion Starter · #1 ·
I posted this problem on another site, and so far haven't gotten much help. Probably because it sounds so screwy that noone has any idea of what to even suggest. So, I thought I'd post here hoping that someone might have ideas on how to fix this problem or suggest a course of action.

Post from the other site, copy and paste.

Now I'm not one to come running to this forum with the slightest problem, but as I said I am at a loss and I need help, and I'm getting frustrated.

I bought a new 14.5" stripped upper, carbine gas system. I won't identify the company yet, but it is considered by most a top tier company, and I'm not sure if the upper is at fault.

Bottom line is that the gas key (on the carrier) gets "clogged" after firing just one round. With the key clogged that leads to a variety of problems, you name it I've experienced it. I've swapped out every part, and the problems change, but it still will not run reliably. Bottom line if gas isn't getting inside the carrier the rifle won't run, simple as that.

Today, I went to the indoor range to test, thinking I had found the problem when I discovered the gas key "clogged" and cleaned it out. Nope, first round and it clogged again.

So I swapped the bolt carrier group, and that one clogged up too. It is carbon clogging it I think, because CLP in the key disolves it in a matter of seconds.

I've tried PMC Bronze and XM193, same problem.

The first bolt that clogged is a chrome bolt that has been lightly used in another rifle, and it never failed. The second bolt I tested today was brand new, first rounds ever fired through it.

I'm at a loss! All I can think to say is HOW! and WHY!

Any and all thoughts appreciated.
 

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Discussion Starter · #4 ·
"clogged" as in unable to blow air into the carrier with my lips, bolt removed of course. I can clear the clog sometimes with canned air, sometimes it takes a blast of Gunscrubber. Another odd thing is that after i've cleared the clog, I can put the bolt back in the carrier, pull the bolt out, blow into the key and the key is clogged again. Go figure on that one.

It's hard to erase the clogged key from my mind because I think it is key to problem. A normally gassed carbine should have enough pressure to blow/burn out any carbon that may collect in the orifice, so my working theory at this point is undergassed.

The problems are short stroking, failure to eject, double feeds, you name a problem along these lines, I've had it, literally. I have tested with two BCGs and while each carrier exhibits the same problems, the severity changes with each BCG. AND both carrier keys clog.

For the record I have tested with different buffers, ST-T2, H and standard recoil spring.
I blew the gas tube out with Gunscrubber and air and it seems to be clear.

This is an odd one, thanks for the help
 

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Are you sure your gas tube is correctly inserted?
 

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Like I said. Ignoring the "clogged" gas tube, your symptoms indicate poor gassing. The gas hole is either the wrong size, or your gas block/front sight base is installed incorrectly. Is it PSA? I have heard that in addition to taking forever to ship, their quality has also taken a dive. A lot of people having to return stuff due to malfunctions. If they take forever to get you your stuff the first time, I can't imagine how long it would take them to fix and get something back the second time.
 

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Check if gas block hole aligns with hole on barrel. Usually when you remove has block you can see a "halo" where it's hitting. While you have the gas block removed, remove gas tube and run a pipe cleaner through it the full length. Best suggestion so far is to let manufacturer deal with it since it's their responsibility.



Ex Umbris Venimus
 

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The problem isn't your bcg. Too small gas port, obstructed gas tube or port. You have so little pressure getting to your bcg that the carbon is just being deposited there rather than being blown out like normal.

Your description says BCM to me. Either way, return it.
 

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Discussion Starter · #12 ·
Thanks for the replies everyone. To answer and respond to posts.

The carbine is new, so I assume the gas tube was installed correctly by them, visual inspection says yes.

Not PSA.

Since I didn't build it, I'm not going to take off the FSB or replace the gas tube. If I determine that the upper is the problem (just about there) then it will be sent back for repair or replacement. As said, it was only yesterday that it occured to me that the upper might be the problem.

Wahoo95, thanks for the offer, but it would be late next week before we could get together, by then I hope to have it on the way back to the manufacturer.

Jerz, we're saying the same thing about the gas port. and :)

Again thanks to all who responded.
 

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Are you reloading the rounds you are shooting or are they store bought? A long pipe cleaner and some carbon cleaner should clean the issue. But if it is stopping up after one round then I would have to check the ammo you are using. I just can't see it stopping up after one shot. Maybe after 5000.
 

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Discussion Starter · #14 ·
Wow, this one was dug up from the past.

Sorry I forgot to update it.

Turns out it was the front gas key screw, it sheared off. I sent the carrier back to the company I bought it from and they replaced it.

Problem solved.
 
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