I recently put together an AR with a bushy lower, bolt assembly, 14.5 in heavy barrel fluted with ycomp, and charging handle.  I used a Rock River tactical upper for the build.  Here is the problem--first time out with the rifle for sighting, the first shot fired left a spent casing in the chamber with a portion of the casing rim ripped off by the extractor.  I tapped out the casing with a cleaning rod, and was able to shoot 10 rounds or so before it happened again.  As I continued to shoot the failures began to space out with a full 60 rnds before the last failure.  

Correct me if I am wrong.  It appears that the bolt is attempting to extract the casing too early in the cycle, resulting in a bulged case that gets "stuck" in the chamber.  I here this is a common occurence in shorter barreled uppers.  How can I correct this other than purchasing a pigtail gas tube?

By the way, the rifle was correctly headspaced and thoroughly cleaned prior to firing.  Sorry about the long post. Thanks...

Are you using reloads? Sounds like the ammo you're using isn't sized enough for the chamber. The bolt doesn't close completely(although it may appear so) and the bolt is unlocking and pulling the rim before the pressure is all abated.
This can happen with a tight chamber and high side of tolerance ammo, or ammo that was not resized with a small base die. My .02.

I'm using south african surplus

spy590,

Before we assume that everything else in your rifle is hunky-dorry, check that your empties are not showing any signs of excess pressure - blown or pierced or cratered primers, expanded case heads, a button of brass extruded into the ejector hole, etc. High pressures will make a rifle extract hard...

I too am a proponent of polished chambers for reliability in all autoloading rifles. Flitz on a mop, a small dowel split with 220 wet-or-dry and oil, fired case threaded for a cleaning rod and toothpaste, whatever. Just do the body and maybe the shoulder - when you get into the neck it is way too easy to get into the throat and you do not want to do that.

I do mine with a dowel turned to the taper of the body only and 220 grit, wet with oil, clean up, then use a case fired in that rifle with a drill and toothpaste. No, you do not need to be any finer than that.

The pigtail looks like terrific idea - It makes the rifle wait longer before opening. You might have to enlarge your gas port with it...

Thanks guys, There is a slight bulging of the case head.  That's what made me think that the rifle was attempting to extract too soon.  However, it seems to have smoothed itself out, but I think I'll give the chamber a polishing anyway...

sounds alot like your using 5.56 nato ammo in a .223 saami chamber. Try some american manufactured .223 ammunition.

Did you clean the camber before you went out for a test drive? If it "fixed" itself that is my guess.

I have a Colt Sporter Match AR with a Fulton Armory M4 type HBar Match barrel, and I have the same problem. The shell gets stuck in the breech after about 100 or so rounds. The area of thye shell that the extractor grabs rips that section completely out. I also use the South African 5.56 ammo. The Fulton barrels are said to be made to accommodate military rounds (a deeper throat).  

I had three FTE with SA ammo out of 1/2 battlepack. 2 were out of an Armalite M15-A2 and one was from an Eagle Arms EA-15. Neither barrel says what chamber they have, the receivers say 5.56mm, I assumed they were milspec. Does anyone out there know? I haven't polished the chambers yet.

I have a RRA 16" pre-ban upper. I have a shell get stuck in the chamber several times with the case rim ripped off where the extractor catches it. The one constant is that his only happen with S.A. 1988 mfg. What lots were you guys using? Maybe it is just a bad lot.

The stuff I was shooting was Ball M1A3 lot#
605 A 87. Headstamp was 87 and 13.Is this stuff the same as M193?

Same problem here with my DPMS M4orgery upper.  I was using S.A. battle packs and it failed to extract about every 4-5 round.  The extractor ripped the rim right off.  The case was about 1/4 of the way extracted(ie., 3/4 of the case was still chambered.).  Same thing for me, polish the chamber?

Thanks!

I cleaned my chamber and bore before firing.  I have a Bushy barrel so it should have a Nato chamber.  I used the same lot of S.A. in my bushy sixteen and had no problems, only in my new rifle.  However, my bushy sixteen has had quite a few rounds through it so the chamber is probably nice and smooth...Hopefully its just a bad batch of S.A. ammo.  I'll check the lot number and see if it matches what's already been posted...

There is obviousley some kind of problem with this SA ammo. I have the FTE's that occur the same way, ripping case rim. And ONLY with SA. Why is it that all of us have the same problem with only this ammo? It has to be the ammo. USGI ammo does not do this in my weapon. My brass looks fine , no bulges. I have lot 351A 86
This ammo is cannot be made as well as our USGI ammo.

I haven't been able to detemine if I've got mil-spec chambers, my barrels aren't marked. I'm going to try some other ammo and see what happens. Lots of other people on this board love this stuff, I'd like to love it too, it's cheap.

My lot No. for S.A. is "637 A 87".  This pack is unopened but it should be the same lot as the one I was using because I bought them both from AIM(if I remember correctly) at the Bulletfest and they were from the same case.

The lot # on mine is 817A88Z. I have had no problems with my new batch of 375A/86

Commonly, if the barrel isn't marked with 5.56 NATO it isn't. It is .223 SAAMI. Eagle Arms is .223, Armalite (until recently) is also .223.
Go to Armalite's website, they say it right there, .223 SAAMI.
I shoot the same lot SA ammo as you guys are thru my Bushmasters, they are 5.56 NATO chambered and
I have flawless shooting with the SA BP ammo.
Most Wilson barrels, if not marked, are .223 as well.