Ar-10 Sticking Brass and Live Rounds

[pdt1793db]

So I acquired a custom built ar-10 on a trade. Took it to the range, loaded it up with reloads that work great in my Remington 700, bang, action cycles, no casing ejected, and next round in the magazine was fed into the back of the spent casing sticking the action open. So I cleared it, took it home, and removed the casing. I inspected the other live rounds and they were in proper dimensions when checked with my head spacer. So I run some Federal Sierra Match Kings in it from the factory cycling the action not firing. Action still locks up but not as bad. I then noticed markings on the shoulder. Just to make sure it was not the bullet getting stuck in the rifling I ran a casing with no bullet that was in spec. Same markings in the shoulder same locked up action. So I'm thinking my chamber is to short and needs reaming. Thought I'd see what you all thought before proceeding. Any Ideas?

[precision_shooter]

Sounds like it wasn't properly headspaced by whoever built it.
This is why I don't buy other people "builds" or "parts guns".

[mehavey]

1. Do you have a Hornady Case Headspace comparitor ? (and can check the dimension of the factory loads)
2. Do you have (or know anyone who has) a 308Win 'GO' gauge ?

Either way, an easy (but irritating) fix.

[243winxb]

The bolt and barrel should be made by the same company.

[HiBC]

Well,you do whatever you think is right.I do think its always a good idea to verify headspace if there is any question....
But I don't see failure to extract as necessarily a headspace problem.
You might be checking the tire pressure because the oil pressure light came on.
The flag I see is "reloads that worked fine in my Remington 700."
Your AR-10 is not your Remington 700.
No doubt as a handloader you began with a recommended starting load and worked your way toward max for your Rem700.
Why would you not show your AR-10 the same courtesy?
Brass resized to fit your Rem may be long for the AR.
My brother has a perfectly wonderful ArmaliteAR-10-T. He wore out the original Badger barrel and replaced it with a Kreiger.With the Armalite installed Badger barrel,Portugese surplus 7.62 ammo that chrono'd 2900 fps (a bit hot! Maybe why it was "surplus"....or reject) would fail to extract.
It worked fine in my FAL.
If your Rem700loads are a bit zippy,they may extrude brass back into the ejector .The sharp edge of the hole in the bolt face will scrape slivers of brass into the ejector.Check to see if the ejector works freely.

You now have a gas gun,and a new set of rules to play with. The pressure curve is key to function. Your Rem700does not care about pressure curve.

Proper handloads can work fine. 168 gr Matchkings or Nosler Comps can be OK. Varget is a good powder.Don't push the Max thing.Be content a grain or two short.
But,for a starting point,I'd get some 168 or 175 gr match factory loads. Brass case,USA. See if they shoot.

If they do,you have confirmed an ammo problem.

But its good to check headspace.Be sure to clean the chamber first.You might see if Sinclair has a bolt disassembly tool.And youmight want a spare extractor roll pin,extractor spring,ejector,and ejector spring.You strip the bolt to check headspace.Part loss is possible

Also,when you reload for asemi,setting up proper case "head clearance" when you size is critical.

[Nathan]

You need a 308 GO Gage.

[ed308]

Sounds like a gas, ammo, ejector or extractor problem. Like HiBC suggested, see if it runs with factory ammo. When it comes to ARs, always a good idea to test a newly acquired AR with factory ammo before moving on to reloads. But I would check and make sure the extractor still has lips and springs back into to position when pressed. Also check and see if the ejector springs back. Make sure nothing is trapped in the spaces and keeping them from working properly. If that doesn't fix the problem, move on the gas system to make sure your AR is getting enough gas to cycle the AR. I would start by checking to make sure the gas block is properly aligned, no leaks at the gas key, adjust if it has an adjustable gas block and etc. Also scrub the chamber to make sure its clean.

I don't agree having the a bolt and barrel made by the same company is important. It's unlikely the AR is not head spaced properly. Not saying it can't happen. Just not likely.

[mehavey]

Originally Posted by OP

So I run some Federal Sierra Match Kings in it from the factory cycling the action not firing. Action still locks up but not as bad.

But I don't see failure to extract as necessarily a headspace problem.

Sounds like a gas, ammo, ejector or extractor problem.

The OP didn't cite an FTE problem (after the 1st failure to eject). He cited a cartridge locking up the action when it slammed home -- even with factory ammunition.

That's a classic headspace problem in the AR (to be confirmed by use of a GO gauge.)

Straightfoward fix.

[navajo]

Had two problems with Armalite AR 10s. Two out of 6. One turned out to he a magazine with too much phosphate inside, simple fix. Factory built gun.
The second was a garage built gun which was priced too low to turn down.
First problem was a rifle length buffer in a carbine tube. Easy enough fix. Seconde took a bit of investagating. Short stroking. Replaced extractor, didn't fix. Replaced ejector and spring, didn't fix.
Removed gas block. TaDa! What came out looked like gear oil and there was a lot of it.
Cleaned block and tube, reassemble and never had a malfunction again.
Have a look at your gas block. You never know.

[bfoosh006]

How many rounds has the rifle fully fired ?

AR10's need a break in period, in particularly at the bolt and receiver extension....and.. and since there is no milspec guidelines, not all parts mesh as seamlessly as AR15's.

Is the bolt NiB by chance ?

Next....if the action is cycling to fast and the chamber pressure is still under high pressure, the extractor might be popping past the rim.. What do the case rims look like ?

How hard is it cycling ?

[pdt1793db]

My understanding is that the rifle had 5 rounds test fired through it and that was it. So pretty much a brand new gun. Which leads me to believe the chamber is new also. The break in makes since. I did not keep the one round I fired separate. I was pissed and threw the casing in with some others in the heat of the moment. Maybe I should take the gun. 100 rounds, mallet, rod, and magazine and just shoot it a bunch and see if it breaks in some. I hate beating the hell out of my brass like that but it seems like that might be an option.
http://s1183.photobucket.com/user/pd...&page=1#upload
This is a picture of the casing that I resized and tested.

[mehavey]

You did say that unfired commercial ammo "stuck", right?

Any rifle where new/unfired commercial ammunition sticks in the chamber from simply cycling the bolt -- ain't gonna get better with age.
Go get a GO gauge check before taking a hammer to things trying to repeatedly drive cases out of the chamber.

[HiBC]

Agreed,check the headspace.You willstrip and clean the bolt and chamber to do that.

But then function check with brass USA grade military or match ammo.

[pdt1793db]

Yes the unfired commercial grade stuck

[HiBC]

Certainly .308 reamers and gauges should not be rare.
While it might seem simple,there is quite a bit of experience based "feel" and technique to running a chamber reamer in.One chip straddles a cutting edge and your chamber is ruined.There is more. Its not for the inexperienced.
I would probably use a reamer and a tap handle to touch up the chamber if a headspace gauge said it was necessary.
Another option is a pull through reamer.The bolt rests on one end,and the reamer is turned via a rod from the muzzle. When the bolt goes into battery,you are done.
I only have one experience with this outfit.It went OK. I will give you a link as a resource. I don't have enough experience to endorse or review either way.

http://www.reamerrentals.com/SearchResults.asp?Cat=87

[bfoosh006]

"Any rifle where new/unfired commercial ammunition sticks in the chamber from simply cycling the bolt -- ain't gonna get better with age.
Go get a GO gauge check before taking a hammer to things trying to repeatedly drive cases out of the chamber. "



The chamber won't change... but the locking lugs and bolts locking lugs could.. especially if it is NiB coated.... and the bolt face is what decides headspace as much as the chamber.

Make sure the chamber is very clean.. prior to checking headspace.

And a mallet and hammer to remove a chambered loaded round is a no-no... there have been numerous documented cases that smacking the bullet have caused a disastrous discharge.

For a AR type weapon, you need to move the Bolt carrier first... so prying from the ejection port or magwell is better... with a flat screwdriver.

[bfoosh006]

All 3 of my .308 barreled uppers were very sticky extracting when "brand" new.

I ended up thoroughly cleaning the chamber, then polished the chambers slightly... that helped enough to get the .308 AR's functioning properly.

It was VERY important to clean the chambers first !!
Nitrated barrels typically have a grunge from the process. And most ALL barrels are delivered with a protective "oil" from the factory... all mine did.

Your upper might have a headspace problem... I thought mine did until I checked the headspace on all 3. All of them would chamber the "Go" guage.

And would not chamber the "NoGo" guage.

After firing a few dozen rounds, mine all work perfectly now... even with the added adjustable gas block turned to 6 of 12 clicks ( half the gas volume ? )

The reason I ask about the case rims, is because if yours is cycling fast and hard ( typical OEM configuration, LOTS of gas volume from a .308 round ) your rifle might be trying to yank the spent case out while still under a lot of chamber pressure.

Prior to the added adjustable gas block... my cases all showed excess chamber pressure signs... ejector smear, extractor markings and stiff extraction... after the SLR adjustable gas block... all that went away.

The SLR gas block was allowing extra milliseconds of a locked bolt and with that it allowed the chamber pressures to drop just enough to lessen the chambers " grip" on the case.

I do suggest you have the head space checked for your own "mental peace of mind" and for sake of safety , but do think your .308 AR just needs some tinkering with.

If you are interested... I have a rather lengthy thread about my PSA PA10 GenII experiences and is improvements I did quite easily to turn my $700 AR10 into a tack driver with ammo it likes... ( including cheap DAG surplus )

Here is the link....https://forum.308ar.com/topic/15124-...-observations/



HiBC said it very well.... "The pressure curve is key to function. "

So consider getting an Adjustable gas block as well... it truly changed every .308 upper into a much more pleasant "persona"

[ed308]

I've had similar problems with a new ARs with cases sticking, not chambering and not ejecting. Usually lube and break-in clears up the problem. My 270AR that started with this problem after 100 rounds. I eventually fixed the problem by scrubbing and polishing the chamber. That helped but didn't completely fix the problem. When I tore down the AR, I found the lip on the extractor was partly torn off.

If a new barrel and the bolt, it's unlikely to be a head space issue. If the bolt or barrel is worn out, then it might be a headspace problem. Since AR barrels slide into the upper and aren't screwed in like a bolt rifle, if the barrel is properly inserted into the upper and torqued down, then headspace should be fine. But check head space if you feel the need. If you determined the bolt and barrel aren't properly head spaced, try it with a different bolt. Thats what manufacturers do. Other than that, not much you can do to fix a head space problem.

[pdt1793db]

Well I spoke with the builder yesterday. He said he would take care of it and is going to make it right. So lets hope that follows through.