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Discussion Starter #1 (Edited)
Greetings...
First post here for me. Has any run run into this problem: I just put together a 6.8 spcII. The barrel is from ???, has a mid length gas system, low rise gas block, aero upper, mil spec BCG. The lower is a spikes with 6 position butt stock. Standard weight spring and buffer. My problem is that the damned thing won't cycle. I have used the same lower set up on both my .300AAC and 5.56 and never ran into a problem. I have tried remington ammo as well as Hornady. There is no binding on the gas tube and cycling the bolt by hand it is smooth as silk. Do you think I need a different weight buffer? Could it be short cycling? I'm almost tempted to put a cam next to it on the bench and record the action to see what is going on. Any thoughts would be greatly appreciated.
 

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Put 1 round in the mag and see if it locks back on an empty mag after firing.. Did you scrub the chamber good?
Have you checked to see if the gas block is aligned properly?
 

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Need more info other than not cycling.

Does it extract, eject and not pick up the next round? Or does it extract, but not eject or does it not do any of it and the spent brass is left in the chamber?

A standard buffer and spring is "always" where to start. The most common problem is the gas block not properly aligned with the gas port in the barrel.

As stated above. 1 round in the magazine chamber and fire. What happens to the spent brass?


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What exactly is it doing? When you say it wont cycle does the bolt move at all? Does it not move far enough to eject or strip another round? A little more info would help.
Edit: When I started typing only there was only the OP. Phone rang and 3 more posts popped up before I finished posting.
 

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Discussion Starter #6
Wow talk about a fast response. Thanks guys. Ok here is what happens step by step. With mag in it strips and chambers fine. Upon firing it WILL NOT eject, doesn't even seem to try. When I cycle by hand it strips and feeds. Yes it locks back with only one round when cycled by HAND. one thing I did notice is that there is a lot of gas/smoke from the front of the upper when fired.
 

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It extracts? But does not eject?

If it doesn't extract it of course will not eject. Placing 1 single round in the magazine charge it and fire it. Where does that fired brass go? Still in the chamber, or extracted and weakly let go remaining in the upper?


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I think he means it doesn't extract, sounds like a complete lack of gas flow. Gas tube severely misaligned or as I seem to recall seeing one time, gas tube put it upside down. Or is the bolt opening but the round staying in the chamber?
 

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I think he means it doesn't extract, sounds like a complete lack of gas flow. Gas tube severely misaligned or as I seem to recall seeing one time, gas tube put it upside down. Or is the bolt opening but the round staying in the chamber?
I'm compelled to think the same.

I think your attention needs focus upon your gas block and gas tube. Making sure there is no obstructions and all are properly aligned with the barrel gas port.
If you have a loose fitting gas block to barrel you may be losing a lot of gas there causing your cycling issues.


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I'm compelled to think the same.

I think your attention needs focus upon your gas block and gas tube. Making sure there is no obstructions and all are properly aligned with the barrel gas port.
If you have a loose fitting gas block to barrel you may be losing a lot of gas there causing your cycling issues.


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You know what they say about brilliant minds.
 

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Discussion Starter #12
Ok would like your thoughts. I had bought this upper as a complete "build". Only thing I did was put it on one of my lowers. I just took it apart to see what was going on. See the pics. It appears that there are a few things going on. 1) this appears to be a DPMS barrel that ORIGINALLY had an A2 front sight that removed and a low profile gas block installed. There is a whole lot of gas blow by and cutting. See pics. I personally have only put about 20 rounds through it and not one of those came out of the chamber on their own. Any thoughts on what I should do. I sent the seller a rather lengthy and pointed email about this build and what I found.

With that being said. Is the gas block which is on it going to work? It would appear that it was misaligned from the get go from the amount of gas to the left of the hole. I put everything back together and am going to go out in a bit to see it helped anything.

I am trying to upload pictures but it won't?
 

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Discussion Starter #13
IMG_20150913_124234_1.jpg Ok would like your thoughts. I had bought this upper as a complete "build". Only thing I did was put it on one of my lowers. I just took it apart to see what was going on. See the pics. It appears that there are a few things going on. 1) this appears to be a DPMS barrel that ORIGINALLY had an A2 front sight that removed and a low profile gas block installed. There is a whole lot of gas blow by and cutting. See pics. I personally have only put about 20 rounds through it and not one of those came out of the chamber on their own. Any thoughts on what I should do. I sent the seller a rather lengthy and pointed email about this build and what I found.

With that being said. Is the gas block which is on it going to work? It would appear that it was misaligned from the get go from the amount of gas to the left of the hole. I put everything back together and am going to go out in a bit to see it helped anything.

IMG_20150913_125223.jpg IMG_20150913_125232.jpg IMG_20150913_125903.jpg
 

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While you had it off, did you look through the set screw hole to make sure the gas port in the gas tube was in line with gas port hole in the gas block? You could have a mis-alignment there which could lead to the gas being push off to the right as indicated on the barrel. You can use some blue loctite carefully applied so not to block the gas ports to the barrel and gas block to make a seal. The gas will take the least path of resistance and a poor or loose fitting gas block will result in lost gas that's needed for functioning the weapon.


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Looking at the first picture from the OP, the gas tube appears to have the bend in the right direction, so it's probably not upside down, but could have the hole out of spec and to the side. Also, take a scotch brite pad and clean the gap journal and inside of the gas block really well. All that crud on the barrel will keep from forming a good seal. Take some compressed air and shoot it through the gas tube to check it.


-Alexander
 

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Guys!! He has a front sight block on first, so the barrel was drilled and pinnned. The barrel will not have a dimple for a set screw type block since the barrel was drilled for the FSB.

To the OP get a clamp on style gas block and make sure the holes are lined up. Or convert the FSB to a poor man's lo pro, there are plenty of vids on YouTube on how to.
 

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Guys!! He has a front sight block on first, so the barrel was drilled and pinnned. The barrel will not have a dimple for a set screw type block since the barrel was drilled for the FSB.

To the OP get a clamp on style gas block and make sure the holes are lined up. Or convert the FSB to a poor man's lo pro, there are plenty of vids on YouTube on how to.
He doesn't have a front FSB, from his post it was converted to a low profile gas block in which he was unaware until he took it apart. What he has will work if properly installed with no major leaks.


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He is assuming that it had an FSB because of the dual rings on the barrel where they didn't bother to finish under the gas block but it is a DPMS barrel and it was likely a railed low pro clamp on block in its original form. It would still be nice to have the dimple to align the gas block but not absolutely necessary. You can't see any signs from the pics that it was ever drilled and pinned but I am willing to guarantee that gas block alignment is the the problem.
 

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Discussion Starter #19
For the ESS I was thinking of my .300 I just put together. When I wrote ??? I had yet to take the block off. Yes it had a pinned on A2 sight. See attached side profile. I just spent the last 2 hours out screwing with this. I would fire around and nothing. Acts like a gas block that can be regulated and is turned off. I removed hand guard so I could loosen and move gas block a smidgen one way or the other to see if it made any difference. Nothing. Goes bang and case is still in the chamber like it didn't want to move at all. Got to the point of taking a vid firing it from my cell to see if it even tried to cycle. Nothing, see attached pic and vid. I just sent the guyI got the thing off of a rather long E-Mail ( and I didn't even cuss :) ) He says every one of his uppers are test fired 2 times prior to shipping. Yea right. I'm an 07 and have NEVER ran into this sort of thing with anything I've put together. No way it was test fired prior to shipping. Not sure how to up load a video. IMG_20150913_124205.jpg
 

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For the ESS I was thinking of my .300 I just put together. When I wrote ??? I had yet to take the block off. Yes it had a pinned on A2 sight. See attached side profile. I just spent the last 2 hours out screwing with this. I would fire around and nothing. Acts like a gas block that can be regulated and is turned off. I removed hand guard so I could loosen and move gas block a smidgen one way or the other to see if it made any difference. Nothing. Goes bang and case is still in the chamber like it didn't want to move at all. Got to the point of taking a vid firing it from my cell to see if it even tried to cycle. Nothing, see attached pic and vid. I just sent the guyI got the thing off of a rather long E-Mail ( and I didn't even cuss :) ) He says every one of his uppers are test fired 2 times prior to shipping. Yea right. I'm an 07 and have NEVER ran into this sort of thing with anything I've put together. No way it was test fired prior to shipping. Not sure how to up load a video. View attachment 13758
Take the gas block back off and as someone recommended earlier, take the rear set screw out and look through the hole and see if you can see the hole in the gas tube through the gas port in the top of the gas block.
I read DPMS but was thinking something else. I realize that DPMS doesn't use any clamp on blocks on their factory rifles, only pinned or set screw.
 
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