So I finally have all the parts rounded up to assemble a different AR10 upper for my existing AR10 rifle. All I lacked was a gas tube and delta ring kit. Go to order on Armalite's website and they're OUT of gas tubes. Does a standard AR15 tube work? I have no idea. I don't know if I should sell this thing and get another type of AR10 that I can actually get parts for...or wait.

Armalite may have them in stock and just didn't update their website, call them. If Armalite doesn't have any in stock Fulton Armory has the longer rifle length tube that will work on the Armalite in stock.

ETA:

https://www.fulton-armory.com/gastuberifle-1.aspx

Try it with the regular tube - its only about 3/16" shorter.

It won't hurt anything other than maybe short stroking. In that case try a lighter buffer or spring.

Let us know how you make out.

Bad advice, it’s not going to work. Many have been down that road to no avail. Wait and find the right one....

Some people just dont shoot their stuff..

Gas port location further out in order to use USGI style handguards. Fulton offers, or used to off the same KISS setup.

I have an Armalite AR-10 upper receiver with a BA barrel (DPMS) with RLG that an AR15 tube worked on, and another Armalite AR-10 receiver with a Wilson Combat barrel (DPMS) with RLG that required the longer Armalite tube. Both have SLR gas blocks. There seems to be no science...just buy and try lol

That's interesting that Wilson would claim a DPMS pattern barrel that had the 1/4" or so longer Armalite length tube.  I've seen these +gas systems offered on lots of aftermarket barrels for better gas control, but they're clearly marketed as such and do require their own gas tube length.

Looks like as you found out that many/most large frame DPMS pattern barrels will fit right up to an Armalite AR10 receiver.  I installed an 18" 6.5CM DPMS pattern barrel on my B-Model AR10, but it had standard rifle length gas...which worked quite well with this barrel length.

bfoosh, if I'm reading correctly maybe I can answer some of that.  My setup described above with a DPMS pattern barrel with "standard" rifle gas is using my OEM Armalite BCG and the slightly longer AR10 extension tube and buffer setup without issue in an Armalite upper.

The Armalite BCG uses a standard AR15 gas key.  My DPMS pattern barrel, of course, uses an AR15 length rifle gas tube, and my extension use standard AR15 buffers.  My buffer system uses the OEM Armalite spring.

I'm pretty sure the length of the gas tube is somewhat critical.  Too short and you get short stroking.  Too long and you can get contact inside the gas key.  Even when using the right components, we all see how many of these large frame AR's can be a little bit challenging to achieve perfect cycling.  I'd suggest not mixing gas tube lengths that would add another problem.

Yeah. Keep that kind of advice out of the tech forums.

That 3/16" makes a big difference.  I've had to square away rifles that were set up that way before that short-stroked.

An AR15 Rifle-Length Tube is too short, and will cause short-stroke FTEject malfs, gall up the ejection port as the case mouth dings into it, smash brass...doesn't work.

I would try it.  If any thing it will be under gassed.  Report back

Earl, are you saying the actual gas key on an Armalite is shorter or the location on the BCG is back further?...or the whole BCG just sits farther back from the extended bolt?  Interesting.

I know my gas key on my AR10 is an AR15 key.  Putz move on my part when I dropped my BCG while doing the 6.5CM barrel change...Doh!  Had to research what gas key my rifle used.  I'm guessing DPMS pattern BCG use the same gas key?...perhaps?

Edit:  Earl, I see you took those pics down.  Was there something different you found out afterwards?

There is a difference in the placement of the front end of the gas key.





ArmaLite top, DPMS bottom.

similar topic:
arfcom earlier discussion of Armalite gas tubes, although mid-gas length

Lots of  stuff going on here.  Look at the exhaust ports on the bolt carrier.  Gas tube length, gas key length. exhaust port area, among other things, could all determine whether it functions or not, or blows metallic boogers up your nose.

Earl, I thought that other additional pic you had added some different perspective that was valuable...if you could repost that back up.  We've had some interesting discussions and proof about how an Armalite can accept a DPMS barrel.  In my case it worked with an Armalite upper and factory BCG.

Others seems to have mixed and matched DPMS BCG's in an Armalite upper with a DPMS pattern barrel.  It must be that critical components and their moving parts are within some window of tolerance to function properly based on real world examples by posters here.

Earl, on your comment on the gas keys, does a DPMS pattern BCG use an AR15 key or something proprietary?  I know for certain that my B-Model gas key is an AR15 size.  I'd assume that the A-Models use the same BCG.

Gas port location on the barrel determines gas tube length. Armalite uses the longer tube because they offered AR10s with standard handguards for a long time. The larger barrel nut/delta assembly pushed the USGI handguards a bit further, requiring a port drilled further out. Easiest solution to the problem presented. So they drilled ALL barrels this length, to keep things simple. AR10 gas tube, AR15 gas tube.

Gas key location is one of the slight differences, but does not really matter that much. Maybe on a minute scale, but not in overall function. Splitting split cunt hairs basically.

The reason for Earl's differences in the pictures is nominal difference in gas key location only, gas keys are identical. Armalite uses AR15 gas keys, so does everyone else. DPMS specs are a cunt hair different. This wont make a difference really because the gas tube will adequately and sufficiently seal on both, in either setup.

What fucks things up is using AR15 tube on a barrel tapped for an AR10 tube. Sure, it might work more than half the time. It might not. You WILL have issues. You WILL NOT have 100% function. Does not matter what BCG youre using, if barrel is tapped for AR10 length tube, and you use AR15, you will not be making adeqaute seal. You want to have a fresh butthole in prison, not a loose one after your stint.

So, like Duke of White Boy Tacos said, all this shit plays a role. Gas tube seal on gas key, gas tube seal in gas block and on gas port. Adequate sized port under gas key. Properly sized, amount, and placement of side gas vents/exhaust ports. Proper sealing of gas key to bolt carrier. How many mfgs skip that one? Skipping steps to cut down costs, as the undustry knows many people dont actually shoot their shit often enough to really encounter these problems. Will attribute problems to something esle, buying more parts, driving the industry more.

If every mfg built their shit properly, the only ones buying new parts would be those abusing and using their rifles. Indsutry would be kinda stale, and expensive. Supply and demand, blah blah blah.

Look at the detailed differences between Armalite, KAC, LaRue, LMT, Young MFG and compare them to all the DPMS LR308 copies. I dont understand why they all use 2 vent ports, instead of the three. And they are placed differently as well. Specs on this are across the board, no one agrees on shit. We dont see many stripped carriers, Im curious to see the variations in port sizing under the gas key. To me, it seems like a corner to cut to save machine time. Drill 2 holes instead of three. Save on bits and time. Pathetic.

Instead of figuring out a way to make the same quality for cheaper, they cut back on quality to make it cheaper. Bah!

Just use the correct gas tube length. If you dont know, bust out the measuring tape and figure it out. Thats the only way to be for sure.

I use(d) that DPMS type BCG in one of my ArmaLite AR10Bs. (Haven't shot It Yet.)  That is the carrier I had in that MEGA upper you got.  Only had like 100 rounds through it but functioned fine and didn't seem over gassed.  I do have vented adjustable gas block though but I never changed the setting when I went from the ArmaLite BCG to this one. That was with a 26 inch Lilja 3 groove with rifle (ArmaLite AR10) gas tube.

It's been a very informative thread here...thanks for those more experienced in the large frame AR's for putting in and giving some experienced insight.  It's what's great about this site and I guess the internet in general...when you can sift through the chaff.

I guess it just goes to show the potential pitfalls of the large frame AR and mixing and matching various components...and even the success in many cases of mixing and matching.  Some of the details presented here, however, might help in diagnosing some of the potential snafus that can occur.

Oh...and 762AR556...remind me never to share a prison cell with you...LOL!

That upper ended up on the LaRue lower as it needs no mods. Fit is pretty damn nice.

Bcgs are mostly interchangeable.

Kinda surprised no further adjustments needed. But rifle length gas is rather reliable.

Fulton had the gas tubes. Ordered two and got them in this week. Thanks for that tip. And thanks for all the information in this thread about gas systems on various AR-10's. Very informative.

Its not all that simple, but it kinda is. Different ways to skin a cat. I just feel this is a major issue thats being neglected in the industry. I dont really know shit, there could be very good reasons to it. I cant figure it out. But, Im not doing 3d models, fluid dynamics, all that crap. Just observing minute differences.

But thats the major difference that always rang out to me. All these big guys are doing it, but DPMS, basically scaled up an AR15. Kept everything the same, just made it larger to chamber a 308 round. Kinda bass ackwards. AR15 is essentially a scaled down version of the AR10. DPMS scaled up a scaled down version, and lost shit in between.

Armalite and KAC, used older AR10 specs, and made it better. Proper way, right? DPMS, did shit weird. Thanks for it, yeah. Crucial part of industries history no doubt, but dammit man. Update your shit!

On the bends in the gas tube, that is a pretty good point. But, Im not sure if its just being an AR15 tube is to blame, rather than loose specs on the bends. You can get away with alot in this area on the AR15. Definitely a good point, and it does happen. Gas tube putting even a little pressure on the gas key can jack thigns up when firing fast. Shit dont always settle completely by the time BCG chambers new round.

Stick with me, youll be fine. A little tender, but not worn out.