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Discussion Starter · #1 ·
Hello all, this is my first 6.8 build. Got everything buttoned up, and noticed right away, the upper and lower receivers are extremely tight fitting.

Put a mag in, using factory ammo.....
Xm68gd. 90gr gold dots, chambered a round, it fired, but failed to extract, failed to even move the bolt, and it didn't stove pipe or make any scars on the brass.

I'm running a spikes lower, with the M4E1 aero combo upper.
AIM AR/M16 6.8 SPC nitride bolt
ARP 16" 6.8 5R barrel.

Not sure what is going on exactly, just would like some thoughts on it. Thanks in advance.
Brandon
 

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Gas block may be the issue. You may check alignment. Make sure the holes line up.


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the upper and lower receivers are extremely tight fitting.
That is a good thing, gooden tight makes for a more accurate rifle.

Use trigger lube on the takedown pins and use a soft rubber hammer to move the pins a couple dozen times. I use the tip of a full weight buffer.
 

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You stated the gas tube rotated? The gas tube is pinned in the gas block, it can't rotate without the whole block being moved. In your photo the gas tube is upside down.



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

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Discussion Starter · #7 ·
The tube had rotated prior to placing the pin into the gas block. It was in properly, but when it was sit back down on the table, after checking the alignment, it must have rotated and spun around. Then when the pin was placed, I didn't think it needed to be checked again after I sat it back on the table.
 

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You stated the gas tube rotated? The gas tube is pinned in the gas block, it can't rotate without the whole block being moved. In your photo the gas tube is upside down.

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

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I don't know how everyone else does it but I install the gas tube in the gas block then slide it down the barrel to install the GB. I don't think it's a good idea to place the GB on the barrel then hammer on it even if it is just a little roll pin.
 

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I don't know how everyone else does it but I install the gas tube in the gas block then slide it down the barrel to install the GB. I don't think it's a good idea to place the GB on the barrel then hammer on it even if it is just a little roll pin.
That is what I do as well. I think the time I put it upside down I may have tried to install the GB first then put the tube in. Putting it together first then installing it on the barrel allows me to blow into the tube and make sure it isn't obstructed.
 

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I don't know how everyone else does it but I install the gas tube in the gas block then slide it down the barrel to install the GB. I don't think it's a good idea to place the GB on the barrel then hammer on it even if it is just a little roll pin.
I always install the gas tube in the block 1st as well.

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

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Discussion Starter · #14 ·
That's how it was initially installed, I think when it was held up to the light to make sure everything was lined up, and then sat back on the table. I believe it rotated then, and when the pin was installed the tube was just upside down. It was placed on the barrel after the tube was installed on the block.
 

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That's how it was initially installed, I think when it was held up to the light to make sure everything was lined up, and then sat back on the table. I believe it rotated then, and when the pin was installed the tube was just upside down. It was placed on the barrel after the tube was installed on the block.
Like I said, it happens. Don't let these thugs give you a hard time.
 

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Like I said, it happens. Don't let these thugs give you a hard time.
That is what I do as well. I think the time I put it upside down I may have tried to install the GB first then put the tube in. Putting it together first then installing it on the barrel allows me to blow into the tube and make sure it isn't obstructed.
It happens.
Woodstock is the expert here, listen to him :a32:

you can use a "slave pin" to keep the tube from rotating while you get ready to drive the pin in---the "bump" goes up to the receiver, not down --make sure you have a small gap between the GB and the barrel shoulder unless you are using an original GI style HG



I too always install the gas tube in the block before I put the block on the barrel
 

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Discussion Starter · #18 ·
Haha, it's all good. I don't claim to be the most knowledgeable AR builder out there anyway. This is only the 2nd build I have been involved with, and they are about 6 years apart.

Anyway, I fixed everything back last night after breaking it all down to find the problem. Now, hopefully I can function check things today, and be good to go. Thanks to those that offered advice, everything should run much smoother today.
 

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Woodstock is the expert here, listen to him :a32:

you can use a "slave pin" to keep the tube from rotating while you get ready to drive the pin in---the "bump" goes up to the receiver, not down --make sure you have a small gap between the GB and the barrel shoulder unless you are using an original GI style HG



I too always install the gas tube in the block before I put the block on the barrel
The fat wooden toothpicks work well, not the flat ones. Shove it in to hold the tube in place then let the roll pin drive the toothpick out the other side. I do the same with bolt catch roll pins.
 
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