AR10 build help

[edteach]

I am building my second AR10, the first was a DPMS style and I sold it to my brother, but the one I am building now is an AR10 style. I built he lower on a 80% receiver I made. I ordered a Stag LH 16 inch receiver upper in 308. I had a 3.8 oz buffer in a 7.25 inch carbine tube. It seemed to shoot well but on another forum they all told me if I do not use Armalite tube, spring and buffer for the 308 then it will not work right. I was told that a couple of marks on the buffer tube were signs of it not working well. I ordered the Stag arms buffer and spring for the 308 which is 5.4 oz. I was told on the same forum this was a mistake and I will regret it. I don't see why a Stag arms buffer and spring will not work with a Stag arms upper. Here are some pictures of the buffer I had put in the DPMS I sold.

 

[edteach]

So I would like to know if you guys feel that the Armalite ar10 buffer system is the only one to work as intended or if others are just as good. Thanks for any help. Also here is a picture of the marks the other forum said was showing damage because the buffer was not working well. The photo with the red circle shows where the mark is. The mark is the same place and size on the opposite side.

 

[Mocadon]

That seems to be a CAR-10 2.5" buffer. Check this table out. https://heavybuffers.com/reference.html

I wouldn't think it wouldn't be a problem due to length, but not sure. You can call those guys and I'm sure they'll have some sage advice.

 

[smoothy8500]

showing damage because the buffer was not working well.

Its not a buffer issue, it's the hole for the retaining pin is drilled too far back. The buffer slammed into the pin before the bcg fully closes. Eventually it will break off the pin.

Edit* they have an offset pin that gives a little clearance.

Offset Buffer Retainer for AR-15 Rifles

AR-15 Offset Buffer RetainerThose of you that have had the ‘problem’ know that damaged buffer faces are caused by an out-of-spec buffer retainer pin location or even a bolt carrier. And it doesn’t take much! A ‘beat up’ buffer face is mostly cosmetic, but the more serious issue is if the...

gallowayprecision.com

 

[Mocadon]

Its not a buffer issue, it's the hole for the retaining pin is drilled too far back. The buffer slammed into the pin before the bcg fully closes. Eventually it will break off the pin.

Edit* they have an offset pin that gives a little clearance.

Offset Buffer Retainer for AR-15 Rifles

AR-15 Offset Buffer RetainerThose of you that have had the ‘problem’ know that damaged buffer faces are caused by an out-of-spec buffer retainer pin location or even a bolt carrier. And it doesn’t take much! A ‘beat up’ buffer face is mostly cosmetic, but the more serious issue is if the...

gallowayprecision.com

It looks like that dent isn't on the buffer face, it's on the threads for the tube. I'm thinking the buffer, being a 2.5" CAR-10 buffer, is too short and the carrier is being pushed too far back into the tube. My guess is that it should be a 3" buffer, but without knowing the length of your tube I can't be sure. Call heavy buffers.com or email them. They may want to know the internal depth of your tube, which is easy to measure with the spring removed and a tape measure.

 

[Mocadon]

Measure the inside depth of your tube.
"If you have any doubt measure your current buffer or check the inside depth of your buffer tube. If your buffer is 3-1/4" long and your tube is 7-5/8" deep this is the best buffer/spring combo for your gun."

So, if the tube is 7-5/8" deep you need a 3-1/4" long buffer. If your tube is only 7" deep then your current buffer is correct.

 

[smoothy8500]

It looks like that dent isn't on the buffer face, it's on the threads for the tube.

You're right, I zoomed in and it's not the buffer face.

 

[edteach]

The tube measures od 7.25 inches

 

[Mocadon]

The tube measures od 7.25 inches

Hmm, that makes me think the inside length is 7", which implies a 2.5" buffer, which is what you seem to have. Can you remove the spring and buffer, then gently slide your carrier into the tube and try to see what's impacting the side of the threads? My suspicion is still that something on the carrier is hitting where that mark is. Probably up high close to the bolt area. That shouldn't happen. I still think you should email or call heavybuffers.com. Maybe you have the wrong tube, maybe the wrong spring, etc. My tube on my DPMS G2 system is 7-5/8" deep. You're a AR-10 system so beats me. 7" is a common AR-10 tube depth.

 

[edteach]

I ordered two, one for me and one for my brother Stag 5.4oz and the spring that goes with it. I also ordered one Armalite kit tube and all. So I can do some shooting and see if one works better than the others.

 

[rpoL98]

take a look at the back-end of the fat part of your bolt carrier. does it look like the first pic below, or the second pic? I'd bet it's the first pic. the beveled edges help to prevent that type of bolt carrier impact.

could also be too much gas, buffer spring not stiff enough, or buffer too light. or buffer a skosh too short.

 

[edteach]

I think I will try to file it down a bit on my brothers BCG. Thanks for the heads up.

 

[mtrmn]

IF the gun functions fine other than leaving the marks, it's possible you could just pull the buffer spring out and drop a quarter or two into the bottom of the tube. Looks like the carrier is coming back too far and colliding with the tube. A couple of quarters used as spacers will stop that, but if you put too many in there the BCG won't lock back on the last round.

 

[bfoosh006]

In any typical large frame AR... recoil buffer , spring , and buffer tube recipes. ( Don't mix the parts )

DPMS Pattern....Standard AR15 Carbine buffer tube, 2.5" buffer, ( I use a 308 Tubbs Flatwire ) recoil spring / 308 carbine recoil spring for DPMS pattern.

Armalite Pattern .... Vltor / Armalite carbine buffer tube ( 3/4" longer then a AR15 carbine tube ) , Standard AR15 3.25" carbine buffer, and I still use a .308 Tubbs Flatwire recoil spring. Armalite recoil spring works great as well. EA1095 ( DO NOT use in the AR15 carbine length buffer tube )

( the Tubbs 308 Flatwire fits all buffer tube lengths , rifle, DPMS Pattern, Armalite Pattern )

FWIW.... Lots of manufacturers use the shorter DPMS pattern carbine setup's, Aero, DPMS, PSA, etc... so clearly both patterns work.

As mentioned battering can happen at the lowers RE threads... dropping a quarter / spacer into the buffer tube will work... just make sure the buffer tube is threaded into the lower correctly, and you don't have less then 3/16" space between the retracted bolt face and the actuated mag catch.

IMHO, drill a centered hole in your spacer...( drainage thing )

The battering tends to come from a possibly "weak" recoil spring, A overgassed barrel that needlessly has a vigorous cyclic speed ....a buffer tube that isn't in spec internally ( slightly to long ) ....or threaded in improperly ( needs another full rotation , yours looks fine ) ....or as mentioned, the BCG has the sharp ends shown above ( Thanks to rpoL98 ) ... or a combo all all the above.

The lack of any form of a Mil-spec guideline for Large Frame AR's doesn't help... arrgh. Your issue is a common one in Large Frame AR's.

FWIW... I have numerous Large Frames with both buffer tube patterns in use... barrel lengths from 14.5" P/W through 22" , all with adj. GB's all have been GTG.

So the DPMS pattern does work.

 

[edteach]

I have a standard carbine so I can use a 2.5 inch buffer and spring from Stag that is made for the standard carbine tube.