Stag10 build short stroking issues resloved !! I needed a Armalite gas tube ??

boss351cleveland

boss351cleveland

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I built a Stag 10 in 6.5cm , was short stroking 98% of the time even with the adjustable gas block opened all the way. Tried a new gas block , tried a different BCG all kinds of ammo , no luck . i have a 20'' Faxon Big Gunner barrel, its a DPMS LR308 pattern barrel with a rifle length gas system , also using a Faxon BCG .

I used a rifle length AR15 gas tube but then i noticed the gas tube was not protruding into the upper as much as my AR15 rifles , seemed too short in there .. After some research i found that the Armalite gas tubes are just a bit longer , so i ordered a rifle length Armalite tube installed it and she runs like a champ!! I thought DPMS LR308 pattern barrels and uppers use AR15 tube lengths? or is this just a issue with the Faxon barrel ? Hope this helps someone else .. If your gas tube looks like the one in the top pic get a Armalite tube!

AR15 rifle length tube
31826777427_9041d4e42b_k.jpg


Armalite rifle length tube
31826778487_4b28b814cd_k.jpg
 
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Armalite gas tubes are indeed longer, but not designed for the reasons you've used it above. Armalite increased the length of their gas tubes so that they could build rifles compatible with standard AR15 20" barrel hand-guards.

There are a few things at play here.

Firstly, the longer gas tube was required so that the hand-guard retaining ring, slip ring, and slip ring spring from the AR15 could be used, along with the hand-guard end-cap. The additional tube length was needed because in order to have enough distance for the hand-guards to fit on an AR10, the gas port and gas block shoulder had to be moved forward slightly. If you were to use a standard rifle length AR15 gas tube, it would not protrude far enough into the receiver, and thus not engage the carrier key to provide sufficient gas for cycling.

Second, You're assumption is largely correct... Faxon and other barrels designed for 'DPMS' pattern rifles do indeed use an actual AR15 rifle length tube. Generally, good designs will provide sufficient envelope such that the standard AR15 rifle gas tube overlaps correctly with the carrier key when the bolt is in battery.

The inverse of that, and its hard to say if you would experience this...but if the gas tube protrudes too far into the receiver (honestly it looks like yours does), the gas tube could cause the bolt carrier to not travel forward enough. Effectively you would be bottoming out the carrier key on the end of the gas tube. Again, it doesn't seem like thats the problem given you say it works well now every time. I'm curious to know what the measured length is of the gas tube that now protrudes into your receiver.

Lastly, there is unfortunately no real industry standard for anything 'AR10'. You may have just had a case of things not playing together properly. I'd also say that (and I assume) your 98% of the time is a generalization, and not measured based on X rds of a given ammunition. It's entirely possible that after a number of rounds and breaking all the wearing surfaces in, you're rifle may have functioned completely fine with the original gas tube.

All of the above being said, it looks like you got your rifle working.er
 
As long as the gas tube is not bottoming in the bolt carrier key, I can see how this would help with the problem you reported. More gas is going to be ducted into the expansion chamber.
 
Big JD-From the hills said:
This is good info for us newb builders!! this might be what allot of people are running up against here, resorting to drilling out gas ports and all sorts of dumb stuff.
Click to expand...

Yes.. realistically you shouldn't have to drill out gas ports and other things. The lack of standards simply means things wont necessarily play nicely together all the time. It seems as though a lot of conversations and general information get crossed or confused depending on calibre. .308 and 6.5 creedmoor will have nuances to each system when used in a gas gun, and basing your rifles function on how one caliber works vs. the other may lead to problems too.

I've been working on putting together a large technical report surrounding the AR10s etc, but its not nearly complete yet.
 
I run a Armalite gas tube in my Stag-10 as well. This was brought up a few times in those BCL threads and thats what Criterion recommended on their barrels.
 
Big JD-From the hills said:
This is good info for us newb builders!! this might be what allot of people are running up against here, resorting to drilling out gas ports and all sorts of dumb stuff.
Click to expand...

Usually those people are guys that watch a couple youtube vids instead of doing actual research...lol..

Component selection is Key for AR10s unlike Ar15s not everything will fit or work. and then people cheap out when it comes to gas blocks buffers and buffer springs.
 
tiriaq said:
As long as the gas tube is not bottoming in the bolt carrier key, I can see how this would help with the problem you reported. More gas is going to be ducted into the expansion chamber.
Click to expand...

The ballooned end of the tube is very important at getting a good seal in the key. If the tube is long or short and the seal is Shyte it will not make a difference.

Mil-spec means just that, but it has to be for a specific firearm as DILLIGAF has pointed out because something from an AR15 is not for an AR10 and vice versa. Plus there are dedicated parts for different form factors between AR10 brands.
 
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Yes, the "ballooned" end of the gas tube needs to be a decent fit - otherwise gas will be lost.
It appears to be ballooned, but that is only because the tube diameter has been reduced for a couple of inches. The balloon is the same diameter as the body of the tube.
Just measured a couple of tubes, a new one, and one from a retired competition barrel. The new one had a body diameter of .179" and balloon of .179"; the well used one, .179" and .172". The rifle was still running like a top, but accuracy had dropped off. Thousands of rounds had been fired. This was a .223 barrel.
 
Twan said:
Armalite gas tubes are indeed longer, but not designed for the reasons you've used it above. Armalite increased the length of their gas tubes so that they could build rifles compatible with standard AR15 20" barrel hand-guards.

There are a few things at play here.

Firstly, the longer gas tube was required so that the hand-guard retaining ring, slip ring, and slip ring spring from the AR15 could be used, along with the hand-guard end-cap. The additional tube length was needed because in order to have enough distance for the hand-guards to fit on an AR10, the gas port and gas block shoulder had to be moved forward slightly. If you were to use a standard rifle length AR15 gas tube, it would not protrude far enough into the receiver, and thus not engage the carrier key to provide sufficient gas for cycling.

Second, You're assumption is largely correct... Faxon and other barrels designed for 'DPMS' pattern rifles do indeed use an actual AR15 rifle length tube. Generally, good designs will provide sufficient envelope such that the standard AR15 rifle gas tube overlaps correctly with the carrier key when the bolt is in battery.

The inverse of that, and its hard to say if you would experience this...but if the gas tube protrudes too far into the receiver (honestly it looks like yours does), the gas tube could cause the bolt carrier to not travel forward enough. Effectively you would be bottoming out the carrier key on the end of the gas tube. Again, it doesn't seem like thats the problem given you say it works well now every time. I'm curious to know what the measured length is of the gas tube that now protrudes into your receiver.

Lastly, there is unfortunately no real industry standard for anything 'AR10'. You may have just had a case of things not playing together properly. I'd also say that (and I assume) your 98% of the time is a generalization, and not measured based on X rds of a given ammunition. It's entirely possible that after a number of rounds and breaking all the wearing surfaces in, you're rifle may have functioned completely fine with the original gas tube.

All of the above being said, it looks like you got your rifle working.er
Click to expand...

The gas tube is not bottoming out in the key, no deformations on the tube after 50 rounds fired today , the bolt goes into battery with ease . The AR15 tube was without a doubt the issue look how little in goes into the receiver compared to any AR15. With the AR15 tube i fired 60 rounds or so with only one time it ejected and fed proper and 2 ejections with no feed , the rest were complete failure to ejects. With the Armilite tube is was throwing brass 5 feet , not one hicup in 50 rounds , even with the gas block turned down a few turns .. Not a break in issue , the Faxon BCG is buttery smooth and mates with the faxon barrel extension super nice , I could eject spent cases by hand easy . Feels just as slick as my nicest AR15s.
 
DILLIGAF said:
Usually those people are guys that watch a couple youtube vids instead of doing actual research...lol..

Component selection is Key for AR10s unlike Ar15s not everything will fit or work. and then people cheap out when it comes to gas blocks buffers and buffer springs.
Click to expand...


Not sure what 'proper research' is.... Most info even in this place is 2nd or 3rd or 10th hand info. Hell you could ask most of the retailers on here, stag, or any bbl manufacture what works with what and they wouldn't likely know either.

Yes we need a guide or data bank on what works with what.

Now the question??? where the heck do we all get our 'corect' gas tubes???
 
That was a general statement and not directed at you whatsoever. I was pointing out that there is way too many guys that think ARs should just bolt together and dont realise that sometimes you need some good old trial an error to get things working 100%.

The best way I find to avoid issues is buying what is known to work. Ill usually do a google search for the part I want, for example. " best Ar10 trigger " geissele SSA-E comes out and from there i'll google SSA-E AR10 reviews and follow those links down the rabbit hole and read forums like M4Carbine.net

Go down the list part by part and buy the best one you can afford. Sometime research leads you to some pretty expensive parts . Like those PWS Buffer tubes... lol.
 
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DILLIGAF said:
That was a general statement and not directed at you whatsoever. I was pointing out that there is way too many guys that think ARs should just bolt together and dont realise that sometimes you need some good old trial an error to get things working 100%.
Click to expand...

Oh yeah no problems, it was a general statement/rant on wtf is the best way to go about doing research now adays anyway?? I don't mind youtube as I am more of a visual learner and I can mostly tell that I will like or dislike something if someone has a breakdown/install vid on youtube. Nothing beats first hand/hands on/face to face learning or interaction with experienced people though.

The manufacture/Distributors/retailers realy need to have gotten ahead of this whole deal.... they kind of just threw us a bunch of parts built to some blueprint or another they found and said here.... see if this works??
 
oh hhahaha another beef/rant. I have been away from the internet, and firearms/shooting for some time and have noticed allot of websites, especialy dlask and wolverine have become so brutal for me to navigate??? Some of the service manuals at work have gone to keyword search repair procedure lookup.... and I hate it! I have been using google to search dlask and wolverine websites for products even, as there built in search bar seems to be all but useless.
 
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