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Discussion Starter · #1 ·
Hey guys, i had my adjustable gas block turned down on my 6.8 so it would have the minimum amount of gas to cycle suppressed, and decided that i wanted it to be able to cycle unsuppressed as well. So today i began opening it up turn by turn and testing to see if it would cycle. It seems like the cases are getting stuck in the chamber, as it absolutely refuses to eject and i have to take a rubber mallet to the CH to get it to let loose of the spent brass. Now the adjuster is so open that im worried the hex screw will fall out! This is an ARP 5r barrel with a seekins gas block shooting xm68gd, AIM nitride bcg. I tried lubing up the barrel,chamber, bcg, swapping mags out, and charging handles to boot. All with the same results. However the minute i slap the can on it runs like a raped ape! Any input would be greatly appreciated, this is now the 2nd upper i have that simply seems to not wanna run without that can.
 

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Has your gas block shifted any? I'm not running a can but everything you've described with the FTE sounds like mine when the block shifted.

I wonder if the back pressure from the can is compensating for the lack of gas?
 

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Your gun runs and cycles fine with the suppressor attached?


Sent from a final firing position, the crosshairs are on you!
 

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Discussion Starter · #4 ·
Your gun runs and cycles fine with the suppressor attached?

Sent from a final firing position, the crosshairs are on you!
Yes. With 2 uppers no less. I can have the gas dialed WAY down as long as the can is on either one. As soon as i take the can off, it seems like the adjustment screw is about to fall off and i cant get either to cycle. With my 6.8 it takes alot of force to get the spent shell out of the chamber via hammer, and w the x39 upper it doesn't seem like the cases are stuck, it just flat out wont cycle.
 

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Is the bolt cycling and leaving the brass in the chamber? (Without the suppressor)


Sent from a final firing position, the crosshairs are on you!
 

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Discussion Starter · #6 ·
Is the bolt cycling and leaving the brass in the chamber? (Without the suppressor)

Sent from a final firing position, the crosshairs are on you!
Nope, the extractor has a firm grip on the 6.8 brass, and literally takes a rubber mallet to the CH to make it eject.
 

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Nope, the extractor has a firm grip on the 6.8 brass, and literally takes a rubber mallet to the CH to make it eject.
If the bolt isn't cycling then your not getting gas, check the gas block alignment, check for gas leaks and a clear gas system.

You don't want oil on the chamber either, it needs to be clean and dry

Sent from a final firing position, the crosshairs are on you!
 

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Discussion Starter · #8 ·
Has your gas block shifted any? I'm not running a can but everything you've described with the FTE sounds like mine when the block shifted.

I wonder if the back pressure from the can is compensating for the lack of gas?
Not sure if anything has shifted, it all looks straight to me. I have noticed with a 3rd upper i have, when i adjusted the gas down to run smooth suppressed, it only took about 3 turns on the gb and it was running fine unsuppressed. Have no idea what to do to these other 2 however.
 

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Discussion Starter · #9 ·
If the bolt isn't cycling then your not getting gas, check the gas block alignment, check for gas leaks and a clear gas system.

You don't want oil on the chamber either, it needs to be clean and dry

Sent from a final firing position, the crosshairs are on you!
Roger that, that is typically how i run my ars but in light of this issue i figured it couldn't hurt to try. I'll try to check the alignment when im back at the house. By the way, i had these blocks "professionally installed" and i assume they used loctite on the set screw but who knows. If they did, how would the gas block rotate or otherwise come outof alignment.
 

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Roger that, that is typically how i run my ars but in light of this issue i figured it couldn't hurt to try. I'll try to check the alignment when im back at the house. By the way, i had these blocks "professionally installed" and i assume they used loctite on the set screw but who knows. If they did, how would the gas block rotate or otherwise come outof alignment.
It probably didn't rotate, I wonder if the block is aligned to the barrel port

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Discussion Starter · #11 ·
It probably didn't rotate, I wonder if the block is aligned to the barrel port

Sent from a final firing position, the crosshairs are on you!
Hopefully i can get to the bottom of the gas block problem without removing the suppressor attachment, those things are rock-set on and a total p.i.t.a to remove.
 

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Hopefully i can get to the bottom of the gas block problem without removing the suppressor attachment, those things are rock-set on and a total p.i.t.a to remove.
If the bolt doesn't move with the block wide open then it's not getting gas, the chamber isn't sticky if it runs fine suppressed. Who's barrel is it?

Sent from a final firing position, the crosshairs are on you!
 

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Discussion Starter · #13 ·
If the bolt doesn't move with the block wide open then it's not getting gas, the chamber isn't sticky if it runs fine suppressed. Who's barrel is it?

Sent from a final firing position, the crosshairs are on you!
ARP 5r scout profile barrel. Also i should probably note that its had less than 60 rounds shot through it since i got it new.
 

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Discussion Starter · #17 ·
Well, my day just got really crappy. So, i took off the handguard and verified that the gas block was indeed in the correct position and completely open, loctited the set screws back, left the handguard off and figured to fire a round to see if it would cycle now...and...
BROKE MY BOLT!!!!

Two splits right at the ejector running back into the carrier group. Guess ill be contacting AIM.

Does anybody know what the hell just happened!?! This whole setup has seen less than 70 rounds in its lifespan.
 

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Well, my day just got really crappy. So, i took off the handguard and verified that the gas block was indeed in the correct position and completely open, loctited the set screws back, left the handguard off and figured to fire a round to see if it would cycle now...and...
BROKE MY BOLT!!!!

Two splits right at the ejector running back into the carrier group. Guess ill be contacting AIM.

Does anybody know what the hell just happened!?! This whole setup has seen less than 70 rounds in its lifespan.
Bad bolt.

Was the headspace checked with that bolt as well?

It's most likely fine but just curious.

Sent from a final firing position, the crosshairs are on you!
 

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Discussion Starter · #19 · (Edited)
Bad bolt.

Was the headspace checked with that bolt as well?

It's most likely fine but just curious.

Sent from a final firing position, the crosshairs are on you!
Wait, i pulled another bcg from another rifle and i may have jumped to conclusions. Those two lateral lines at the ejector arent pretty on the 6.8 bcg, but dont look broke compared to the other one. Wish me luck.
 

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Discussion Starter · #20 ·
Ok, the good news is that the bolt isnt broke, and i got it to cycle unsuppressed. I did pull the gb off and totally reset it so that may have been the issue. The bad news is however im having to make a pretty steep tradeoff for the upper to run both suppressed and unsuppressed. As of now it is throwing brass in the 3:30-4:00 area unsuppressed, and in the 1-2:00 area suppressed. That isnt the bad part tho. The bad part is the gas im catching to the face suppressed. I am LH, and have even fashioned my own gas busting CH's and even though i can dial it down to be pleasant to shoot suppressed, to have it cycle both ways its dumping gas in my face like nobody's business. Ah well. What would you do in that scenario?
 
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