stove pipe

I have a 11.5" barrel carbine in semi only. A2 carryhandle upper. All parts appear to be in good shape. I get a stoppage that stovepipes an empty case and traps it above the live cartridge and the bolt with case mouth out. Clearing it it easy enough, but it shouldn't be happening. I think it only happens about once in 40 or 50 rounds. From my experience with service rifles in this family, that's still too many. Most rifles have few if any stoppages as a rule on the civilian ranges. What do you guys think? Extractor? Ejector spring too weak?

Causes? Hmm...

Some stuff to try or look at:

Ammo!
Buffer weight- light, H, H2, H3?
Gas tube worn at the end- usually all on one side
Bolt carrier gas key- worn or loose?
Ejector spring
Barrel port size

Plus a few other odd things, but see where this gets you.

roughly in decreasing order of likelihood. If the bbl. was any shorter, the weapon starts to get finicky or hard on parts, as the barrel port is opened up to compensate for reduced gas pressure dwell time. Yah, it can be done, and is, but...maintenance requirements go up.

Its extracting, so those parts are likely OK, but swap 'em anyway if they've got a fair number of rounds on 'em.

Ammo, some factory some reloads. I think it's only the reloads it happens with. I lowered the load to lower the pressures and that seems to have helped. The extractor was changed immediately and that reduced more. The key is tight. The tube is fine and military issue. I've used lots of those without problem. The buffer is new-old military, like CAR 15. Now the barrel port size is the thing that keeps bothering me, as I can't really check it and don't have numbered drills to measure with. I changed the ejector spring as it was shorter and weaker than a new example. I just wonder if it's not aggressive enough then it won't kick the empty out quick enough.
I'll have to try it tomorrow to see.

More info about the ammo would help a lot:
Brand name info? Bullet wieght?
5.56 pressure?
.223 pressure?
Bullet wieghts , powder type , & charge of reloads ?

For example: I use some old S. Afrikaans 5.56 surplus to test on the higher pressure end and Wolf to test on the lower pressure end of the spectrum.
If an AR carbine will run both S.A. surplus & Wolf 55 grn it's tuned to near perfection.
Some guns won't do it -- the fix is to run a lighter buffer for the Wolf.

The ammo you speak of isn't generally available in Canada. I used mostly reloads with 55 gr sp bullets. 25 gr of Win 748 and CCI 400s. Cases were LC 08. for the most part. By the way, I changed the extractor spring last night and today there were 0 stoppages. Winchester and American Eagle 55 gr fmj's also work perfectly now. I still wouldn't mind a little longer barrel but I'll have to work on that one. Maybe the Calgary gun show.

Thanks for the feedback troops.

I figured this problem out some time ago and thought I would share. The gas port had been open up. The book states the gas port size is .062 and if the barrel goes shorter than the M4 it can be opened up to .0625 but it's not necessary. It apparently made no difference on functioning. SO...I removed the front sight to check size and instead of .062 (1/16" drill bit) the gas port had been opened up to nearly 1/8". Have a look at the difference for yourself. Way excessive gas ! I wire feed welded the hole over and re-drilled it to .062 and it worked like magic. NO MORE STOPPAGES! And it didn't matter what ammo, reloads, factory, military it dropped them in a close neat pile. It was beside the point however, I eventually replaced the 11.5" bbl with a 14" M4 type 9" twist. I have no problems now and only bad memories.

No wonder your extractor/ extractor spring was having a tough time coping! Thanks for the info, that area isn't where most folk would investigate.

When I was an armorer in an Air Force Reserve Security Police Arms room, we had problems with the 11.5 inch GAU-5s (Colt Commando) SOme we opened up the gas hole to .108 to function reliable with the short bullet dwell in the barrel (we would drill progressive from .062 inch. Usually .08 was enough). It was on the excessive size and was hard on gas rings on full auto. That is still WAY smaller than 1/8". I can't even imagine how over gassed that was at 1/8". YIKES!

The hardest thing was on my head. Why don't my gun work? Loading down to low gas pressure was painful. Then when you sit down and X-ray it with your brain, you keep coming back to the same spot. I'm just glad I had an option. I wasn't going to put the longer bbl on until I figured it out. Then of course to share, so these guys with lesser experience have a starting place. Save some time.