AR10 Fail

[twii]

After building 2 AR15's successfully, I figured I might try an AR10, chambered in 6.5CM.  A brief description of my build is Aero Precision upper and lower, BA 22" heavy barrell, low profile gas block, Aero precision BCG in nickel boron, rifle length tube, buffer and spring.  Magpul PRS rear stock.  Finally got the chance to shoot it today and not good.  First try, I loaded 3 rounds in the magazine, after the first shot was fired, the empty round got jammed in the upper, the second round began it's trip into the chamber.  Cleared out all the mess, then loaded just one round in the magazine.  This time, round never ejected.  Bolt catch is holding the bolt back, not the mag.  My first inclination is that the buffer spring is too weak.  Same results with Hornady factory ELD-M as well as handloads with 41.5 H4350 and 140 gr. Hornady Match bullets.   Any help would sure be appreciated.

[flyer]

That looks like your ejector is not ejecting or the extractor is grabbing too hard.

What does your brass look like, specifically the case rim?

It might be embarrassed that you're calling it an AR10.  That's a DPMS LR308 pattern rifle, not the same thing.

Creedmoor's can have gas issues, people usually use some sort of adjustable gas system to tune them.  Since your bolt locked back on the bolt catch, that suggests you have enough gas or too much but I don't think that is your problem.

I would look at your bolt first.

[twii]

After checking things out a bit further, I do belive flyer that you are right about the bolt.  There seems to be a problem with the extractor.  I removed the GCG from the gun and inserted a spent case into the bolt.  I let go of the case and the extractor held on so tight that the case did not fling out.  Seeing as how this thing is brand new and only fired 4 times, I'm sending in the picture and requesting that I send it back for and exchange or for them to fix it.

And yes, excuse the ignorance on the AR10 vs. DPMS LR308.  I guess I still call them all Kleenex. 

[r.tenorio671]

After checking things out a bit further, I do belive flyer that you are right about the bolt.  There seems to be a problem with the extractor.  I removed the GCG from the gun and inserted a spent case into the bolt.  I let go of the case and the extractor held on so tight that the case did not fling out.  Seeing as how this thing is brand new and only fired 4 times, I'm sending in the picture and requesting that I send it back for and exchange or for them to fix it.

And yes, excuse the ignorance on the AR10 vs. DPMS LR308.  I guess I still call them all Kleenex. 

...I do know that the newer nitride BGG's from Aero use a "double spring" in the extractor, one spring insid the other as well as the o-ring.  I would suggest you try removing the o-ring first and retry as the o-ring could be exerting too much tension on the extractor.  if it continues after removing the o-ring, remove the smaller inner spring (assuming you have the dual springs).     I'd also suggest you disassemble the ejector and clean out the channel the spring & ejector fit into, sometimes the crud from the proofing test firing can gunk it up, especially if the bolt sat on a shelf for a long time afterwards.
 

[Stugotz]

And yes, excuse the ignorance on the AR10 vs. DPMS LR308.  I guess I still call them all Kleenex. 

Ah Hell, I grew up here in Minnesota calling every snow machine a Ski Doo! The correct description is a snowmobile!!!   

[flyer]

I mention the AR10/LR308 thing because one of the easiest ways to screw them up is to use incompatible parts.

A lot of people think they can build a large frame AR like they are building an AR15.  The reality is that it takes more care to be sure everything is going to work together.

[twii]

Thanks for the advice and I will check out the extractor closer and see what's going on with it.   

As I was researching building one of large frame AR's, I did discover that there was really no "mil spec" to go off of and yes, you have to be careful of what you are trying to match up.  I believe I did get all compatible components and once I get the thing to function properly, I'll post results and pictures.

[twii]

Heard back from Aero Precision and they recommended removing one of the 2 o-rings and try that.  If that doesn't work, remove the 2nd o-ring.  I started out with both removed and had one extraction failure, replaced one o-ring and seemed to work well.  A few times, the last round did not eject, but most of the time it did.  Still need to "tweak" it some, but at least it's shootable now.  Guess I'll just have to shoot it some more!   

[Cavitation]

update?

[twii]

Finally got things smoothed over.  I had two issues which I believe was caused by component issues.  I was getting 2 large scratches in the case neck and was also getting failure to eject.  BA 22" heavy barrel and Aero Precision BCG nickel boron coated.  The two scratches were caused by rough machining of the lugs in the barrel extension.  I filed down the rough edges on the 2 lugs and slightly rounded and polished it.  Then after reading on another site, I took a good look and feel at the extractor.  With it in the bolt and inserting a case and applying pressure against the ejector and releasing it, the case would bind.  I removed the extractor and filed the very tips round and filed a bit out from the under side of the extractor.  Polished and installed.  Installed the extractor and now insert a case and it will "fling" out when I let go.  I installed the "second" o-ring that I removed thinking the extractor was holding on too tight and went out this past Saturday.  Went though 5, 5 round magazines with no issues at all.  Brass piling up at 2'oclock about 3 to 4 feet away.   Very frustrating over the course of a few months, but I can say I sure learned a bunch.  So that is always a good thing.  Now for load development!

[dadajack]

If I could only get my 308 to feed reliably, that would be cool. Glad you got yours fingered out.

[Velvetant]

If your cases are landing at 2 o'clock it sounds over gassed, they should be landing between 3-4 o'clock.
I would highly recommend an adjustable gas block.

[twii]

It might be a bit over gassed and they probably land between 2 and 3, which is a bit forward.  I am left handed, so ejecting any lower than 3 is not good for me, I'm not going to take one in the face!    I know everybody swears by the AGB, but with a rifle length barrel, rifle length buffer and spring, I would not think there would be a gas issue, but certainly no expert.

[flyer]

Adjustable gas is used to account for loads with different pressure curves.

Companies loading for a bolt action don't care what the curve looks like so some times you want to adjust to the ammo no matter what gas system you have.

[bfoosh006]

It might be a bit over gassed and they probably land between 2 and 3, which is a bit forward.  I am left handed, so ejecting any lower than 3 is not good for me, I'm not going to take one in the face!    I know everybody swears by the AGB, but with a rifle length barrel, rifle length buffer and spring, I would not think there would be a gas issue, but certainly no expert.

FWIW.. try adhering some of the fuzzy side of velcro tape to the case deflector.... it should save your brass from being beaten.

And you might try a KAK Industries 9.3oz heavy .308 rifle buffer, and / or Tubbs .308 Flatwire Recoil spring... if you would like it to be softer shooting.