Gas tube length?

[Thatcoolguy]

Starting my first DPMS 308 build and have a concern on gas tube length.

Barrel is a Faxom 16" gunner profile mid length gas

Upper is an Aero M5

Gas block is Odin works adjustable low profile.

I bought an Aero gas tube in mid length which states it is good for and "AR10" on their website but when I install it, It looks short to me based on what I have read here. The tube measures 11.75

I have found some information out there stating mid length gas tube should be 12.5 but that seems like it would be to long? I have also read that the Armalite AR10 gas tubes are longer but I do not see a mid length on their site. 

Little bit confused hoping someone with more knowledge than I can help shed some light on this

[Thatcoolguy]

Please disregard I have found out what the problem is.

From measuring my rifle and looking at the carbine length Armalite gas tubes I believe this is what I need. It measures 12.0625 so slightly longer than my Aero mid length gas tube.

The "Carbine" in the description had me skipping over that at the Armalite site and once I went back and investigated the length I discovered its actually longer than the mid length DPMS gas tube.

Funny how I have everything stating it is DPMS compatible (Barrel, gas block, receiver) and I need an Armalite gas tube. 

 

Edited March 26, 2021 by Thatcoolguy

[98Z5V]

Correct - and good research.     You need the 12 1/16" Armalite AR-10 Carbine gas tube.  If it's out of stock at Armalite's website, call them on the phone and talk one of the humans there out of one.  If they're TRULY out, then LBE Unlimited makes a gas tube that's 12 1/16", and it works just like the Armalite tube does. 

[mtrmn]

I ran across these at DSG yesterday.

https://dsgarms.com/upper-receiver-parts-arm10007005

[Thatcoolguy]

Thanks for the link that is the exact one I purchased!!

[unforgiven]

Great job all the way around 🍺🍺

[Lr-308FUn]

Well, 
I was on here back in 2019 and I built a AR-10/Lr-308 and at that time I used a 16" Bear Creek Arsenal barrel. Well this time I used a Ballistic Advantage 16" Modern series Government barrel. Things changed with the gas tubes from the first build to this new one. On the BCA barrel I had to use a Armalite Carbine gas tube, cause the standard mid-length gas tube was to short. Now with the BA barrel I have notice that they use the stand AR 15 mid-length gas tube size, I got a Armalite carbine gas tube and it was way pass the cam pin location in the upper receiver, now with the standard AR 15 style mid-length gas tube it was right in the middle of the cam pin rotation area in the upper receiver. 

I think that BCA uses Armalite gas measurements and BA uses standard. Now has anyone else noticed this, cause when building this new Lr-308, using Aero M5 upper and lower set, with the only BCG that I could find from a buddy a Guntech BCG, that had the wrong gas rings installed on it and I got it for a steal, I am hoping when I get the handguard this week and after installation of the HG, that it will headspace correctly, this time I got a set of 308 Winchester headspace gauges. I am crossing fingers that this Guntech BCG will be gtg. 

[98Z5V]

27 minutes ago, Lr-308FUn said:

I think that BCA uses Armalite gas measurements and BA uses standard. Now has anyone else noticed this,

Noticed it?  All the time.  There's NO standard for this .308AR pattern/platform, with all the different manufacturers out there.  Sometimes, a barrel manufacturer will always drill the gas port location in "their standard" every single time - and another manufacturer does it different.  There are even "sometimes" when a specific manufacturer does it one way for awhile - then decides to change...

There's no TDP for these guys to follow, like the M16/M4 platform.  They get to do what they want.  It's not always right, it doesn't always work, and sometimes you have to change up what parts you're using because of it.  That's why we measure the barrel IN the upper receiver before ordering gas tubes, these days.  Or, have both kinds of gas tubes on-hand, so you're ready for any Large-Frame build that you take up.

[Lr-308FUn]

9 hours ago, 98Z5V said:

Noticed it?  All the time.  There's NO standard for this .308AR pattern/platform, with all the different manufacturers out there.  Sometimes, a barrel manufacturer will always drill the gas port location in "their standard" every single time - and another manufacturer does it different.  There are even "sometimes" when a specific manufacturer does it one way for awhile - then decides to change...

There's no TDP for these guys to follow, like the M16/M4 platform.  They get to do what they want.  It's not always right, it doesn't always work, and sometimes you have to change up what parts you're using because of it.  That's why we measure the barrel IN the upper receiver before ordering gas tubes, these days.  Or, have both kinds of gas tubes on-hand, so you're ready for any Large-Frame build that you take up.

Thank you, and I agree that there is NO standard for these rifles, and I think that there should be. Like with my first build, it was a Frankenstein of a build with a mixture of both Armalite and DPMS parts that I was surprised that it even worked, but it did and well. Now this new build having going with what I would call a better barrel manufacture, BA barrel, now having a standard gas tube setup over the BCA barrel using a Armalite gas length setup. I am at this time if I would do another build in like 6.5 creedmore I will be going with BA barrels due to the use of standard AR 15 gas tube usage. 

I did measure but when I did I looked at the wrong set of measures, I had the measurements wrote down for the first build on the gas tube length and wrote the ones down for the BA barrel in the same gun journal I keep for my gunsmithing logs for my own builds, and I looked at the wrong measurement and ordered the Armalite tube instead of the standard mid-length tube, lucky I had a standard mid-length gas block and tube laying around and used that instead. I love having extra parts laying around. 
 

Here is so far my parts list on this build. 

Upper: Aero Precision M5/ with Aero M5 upper kit 

Lower: Aero Precision M5/ with extended take down pins

Buffer kit: Aero Precision M5 enhanced buffer kit 

BCG: Guntech .308 BCG/ Recoil Technologies .308 BCG 

Barrel: Ballistic Advantage 16" Modern series government profile 

Muzzle brake: Strike Industries Jcomp 2 

Gas block: Aero Precision .750 low profile gas block with mid-length Aero gas tube

Magpul K2+ grip 

Magpul ACS-L butt stock 

Handguard, Just Rails 15" light weight M-lok high profile HG

Trigger: Larue Tactical MBT 2-stage flat faced trigger 

Set of headspace gauges from Brownell's 

 

[98Z5V]

12 hours ago, Lr-308FUn said:

Buffer kit: Aero Precision M5 enhanced buffer kit

^^^   That's the stuff that will let you down, right there.

[Lr-308FUn]

Please enlighten me on my folly, with my first build I tried rifle, carbine from a few other manufactures and the rifle cycled like poop, then I switched to the Aero Precision M5 enhanced buffer kit and it ran like a champ, so please let me know your wisdom good sir, thank you.

[98Z5V]

1 hour ago, Lr-308FUn said:

Please enlighten me on my folly, with my first build I tried rifle, carbine from a few other manufactures and the rifle cycled like poop, then I switched to the Aero Precision M5 enhanced buffer kit and it ran like a champ, so please let me know your wisdom good sir, thank you.

Over a decade of building these things in multiple calibers and different barrel lengths, with experimentation, parts purchases, and wasted time and money - makes me choose a recoil system that work with all the ammo all the time, no matter what the caliber/barrel length configuration is...

Not fake parts, not parts that are "like the Armalite parts" - just the real Armalite parts. 

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories&Category=4eeff98b-d9a6-40fd-be6b-ab2e44ec1080

Here's my soapbox on all the shiit that's wrong with .308AR manufacturers, my opinions on what works, through experience, and why some things that are billed as ".308AR parts" will never, ever work right...  

 

 

[98Z5V]

1 hour ago, Lr-308FUn said:

Please enlighten me on my folly, with my first build I tried rifle, carbine from a few other manufactures and the rifle cycled like poop, then I switched to the Aero Precision M5 enhanced buffer kit and it ran like a champ, so please let me know your wisdom good sir, thank you.

A 3.8oz buffer can never function properly in a properly set up .308AR - when that gun was very first designed to run with a 5.4oz buffer.  That's the bottom line.  A 3.8oz buffer doesn't have enough ass to control the mass... 

 

 

Unless you're building some special Race Gun to win money with at competitions.  And then - it's only gonna work with your Race Gun special ammo, and malfunction and choke on other ammo.

[Lr-308FUn]

Thanks for the information, I will be looking into this. I agree, I would really like to get a set standard for the .308 rifles. I have been thinking about this all through gunsmithing school on what direction to go with getting a set standard for these rifles. I would really like to hear if you have any insight on what you think the industry standard should be for the AR10/L4-308? I would like to get this pattern heading towards the Ar15 when it comes to parts and specs but of course at a larger scale. 
Thank you again for all the valuable information. 

[Lr-308FUn]

Also, what would you recommend on my current build, I read that posting and saw several different buffer types, I would like to keep the adjustable stock setup. Thanks for all your advice. 

[98Z5V]

1 hour ago, Lr-308FUn said:

I would really like to get a set standard for the .308 rifles. I have been thinking about this all through gunsmithing school on what direction to go with getting a set standard for these rifles. I would really like to hear if you have any insight on what you think the industry standard should be for the AR10/L4-308? I would like to get this pattern heading towards the Ar15 when it comes to parts and specs but of course at a larger scale.

YOU...  will never be able to change this industry. Never. You can't to a thing about it, but react to it, and fix all the things that need to be done to the Large-Frame AR to make it run right.  You won't make this industry adopt a singular pattern.  If you COULD do that - you would make them adopt the KAC SR-25/M110 pattern.  That was a pure Eugene Stoner design, while working for KAC, and it was adopted by the US Military, as THE standard.  THAT is the only true "standard" out there...   but you won't get other companies to go to that.  Never.

58 minutes ago, Lr-308FUn said:

Also, what would you recommend on my current build, I read that posting and saw several different buffer types, I would like to keep the adjustable stock setup. Thanks for all your advice. 

I already recommended the best recoil system out there.  I even linked it. In the thread I linked, I explained the WHY of it all. 

And, I'm not even a gunsmith.  Imagine that. 

Pass all that information on to all your AR GunSmith Instructors, and tell them to chime in if they think they have other solutions.  I'd love to hear about it.  I'm not being cocky - they're not Eugene Stoner, and they never will be.  None of them can make this platform better than he did. 

 

I'd like to know why you're in a gunsmithing school - and your instructors can't answer your questions.  Why are you here, asking questions?  Your instructors don't know the answers?  

That's because ARs aren't 1911s.  The instructors you have probably don't know anything about building, tuning, or diagnosing gas guns. If they think they do - then bring them aboard, and educate us.  

Edited April 28, 2021 by 98Z5V

[Lr-308FUn]

I am a certified gunsmith but took most of my training in just that 1911s, older firearms as well. I have always been more into custom bolt action and older style firearms like lever actions, shotguns, and the AK 47 rifles. While taking school one course got me into the AR pattern rifles, and I have built several Ar15s but now I am learning on my own since I want to start putting more modern firearm knowledge like the AR-10 platform of rifles, and yes I agree that they won't change the industry stand, I want to come up with a better standard and start possibly in the future making my own designed AR-10 rifles along with 1911s and other platforms as well. 

I looked up that Tubb CWS system on Brownell's and Midway USA and they have been discontinued. I have even tried his website and he no longer sells the Tubb CWS system. That is why I asked what is currently on the market today for these rifles. All that is on his website are AR10 buffer springs. I also agree that I am not Mr. Stoner or John Moses Browning or any other just upcoming gunsmith with ideas and that is what started the firearms industry we have today Ideas. My instructors are at this time no longer available since I have been graduated for about 2 years now. This is why I decided to start another Ar10, cause the AR15 platform of rifles in all its glorious calibers got boring. 

Edited April 28, 2021 by Lr-308FUn

[98Z5V]

1 minute ago, Lr-308FUn said:

I am a certified gunsmith but took most of my training in just that 1911s, older firearms as well. I have always been more into custom bolt action and older style firearms like lever actions, shotguns, and the AK 47 rifles. While taking school one course got me into the AR pattern rifles, and I have built several Ar15s but now I am learning on my own since I want to start putting more modern firearm knowledge like the AR-10 platform of rifles, and yes I agree that they won't change the industry stand, I want to come up with a better standard and start possibly in the future making my own designed AR-10 rifles along with 1911s and other platforms as well. 

I looked up that Tubb CWS system on Brownell's and Midway USA and they have been discontinued. I have even tried his website and he no longer sells the Tubb CWS system. That is why I asked what is currently on the market today for these rifles. All that is on his website are AR10 buffer springs. 

You certainly haven't been keeping up with the information here, and that's obvious.

[Lr-308FUn]

Okay, sure I have read that posting you gave me like 3 times now and I am not sure how we got on the wrong page. I am just going to build it like I did the first one which after some tweaking ran like a champ. I have several different buffer tubes and buffers to try in this new build and I am sure I will figure it out just like the first build. I get what your saying the 3.8oz buffer wasn't designed to run in the AR 10 pattern of rifles, I get that the correct weight should be 5.4oz. I don't even use a stand buffer in my AR15 builds I use mostly the Spikes T2 buffer in all my AR 15 builds with the standard carbine spring and they run at an ejection pattern of 3-4 o'clock. 
Now since I am new at the Ar10 platform is the ejection pattern the same for it as the AR15, I was educated that with the AR15 in 5.56 NATO the ejection should be around that 3-4 O'clock ejection, is that the same for the AR10? 

I currently have looked at this setup as well for this current build  KYNSHOT - Hydraulic Recoil Buffer for AR-10 with collapsible stock (3.25"). I am also considering the Tubb buffer spring also. I have noticed that all current buffers for the Ar 10 rifle seem to be that 3.8oz, and most keep stating to get that Tubb buffer spring. 

 

 

 

[98Z5V]

3 minutes ago, Lr-308FUn said:

Okay, sure I have read that posting you gave me like 3 times now and I am not sure how we got on the wrong page. I am just going to build it like I did the first one which after some tweaking ran like a champ. I have several different buffer tubes and buffers to try in this new build and I am sure I will figure it out just like the first build. I get what your saying the 3.8oz buffer wasn't designed to run in the AR 10 pattern of rifles, I get that the correct weight should be 5.4oz. I don't even use a stand buffer in my AR15 builds I use mostly the Spikes T2 buffer in all my AR 15 builds with the standard carbine spring and they run at an ejection pattern of 3-4 o'clock. 
Now since I am new at the Ar10 platform is the ejection pattern the same for it as the AR15, I was educated that with the AR15 in 5.56 NATO the ejection should be around that 3-4 O'clock ejection, is that the same for the AR10? 

I currently have looked at this setup as well for this current build  KYNSHOT - Hydraulic Recoil Buffer for AR-10 with collapsible stock (3.25"). I am also considering the Tubb buffer spring also. I have noticed that all current buffers for the Ar 10 rifle seem to be that 3.8oz, and most keep stating to get that Tubb buffer spring. 

 

 

 

You obviously haven't done enough research here, GunSmith.  You need to spend some time, look around the board, and research.  Even your

reference of that KynShit buffer has been referenced here before.  

You're just tossing out information that we've all been over here before - but you're putting in zero work to find out any information, that's all right here, right on this board.  I'm not feeding you, when you won't work for food.

[98Z5V]

Everything you stated in that last post of yours - that pretty much cements that you didn't understand the link I gave you before.  You might have glanced over it - but you don't understand it.  As a GunSmith, that should be something that you understand, when you read it. 

[shooterrex]

This works .

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01

I have this on 2 different guns w/adjustable stocks. They run anything I put in them from 147gr to 190gr 308's

 

[98Z5V]

He won't listen, Rex - he didn't listen the first time he was gifted that information.  He's a GunSmith...

[Lr-308FUn]

I have done research on all the information you provide, thank you again and I found the system that I am going with, I will use the Aero M5 kit but modify it when needed with the Armalite heavy buffer and spring. I also have a left over Springco spring from the first build that I can use with that Armalite buffer. If this doesn't work the Aero M5 kit will be removed and the Aramlite buffer kit will be installed, since I order that one last night as well when I discovered that information in the postings on this forum. 

Thank you again, and yes I am a gunsmith that is more familiar with older firearms and pistols. When learning one has to learn to crawl before one walks. I thank everyone for all the information and I will post results on here of this current build. I have also discovered that some of those post covering this subject were several years old, and most of the products that were mentioned in those postings are no longer available, or at least with my searching I couldn't find any in-stock anywhere. 

Thank you have a great day. 

[98Z5V]

12 hours ago, Lr-308FUn said:

I have done research on all the information you provide, thank you again and I found the system that I am going with, I will use the Aero M5 kit but modify it when needed with the Armalite heavy buffer and spring.

You can't do that - not here, with those parts.  You can't run the Armalite AR-10 buffer in that Aero M5 receiver extension.  You'll find out why soon enough.

I keep trying to tell you.  You keep telling me that you read the information that I posted, and directly linked in here.  If you really read it, then you'd quickly understand that what you stated, and I highlighted above in RED - is an impossible combination.  Which is a catch 22 for me - and means you either didn't read my information, or you didn't understand my information.  It can only be one of those two possibilities. 

Edited April 29, 2021 by 98Z5V