7.62x39 upper fails to eject

[flynlow3]

I have a friends ar that is a 7.62x39. It functions flawlessly until it is fired. All brands of ammo stick in the chamber. It is very difficult to eject them. An unfired round goes into the chamber and slides right out. Once it's fired, it's stuck shut.

I've cleaned the rifle thoroughly. The bolt slides freely and silky smooth. I've tried numerous ammunition. Gas block is free of obstruction and alignment is good. Can anyone point me in a direction of why every round that is fired seizes in the chamber and the bolt is stuck shut until forced open? Again unfired rounds chamber and eject flawlessly.

Thanks

 

[hlee]

It is possible that the chamber is a bit rough and holding onto the cartridge. I've had 2 barrels from quality makers that exhibited similar phenomena for the first 20 shots or so. I have a 3rd that I polished with a bore mop mounted on a cordless drill and "charged" with buffing rouge.

 

[rpoL98]

sounds like no gas, or insufficient gas. is the gas tube installed correctly? roll pin through the gas tube hole, not in front of the gas tube? gas tube not upside down? if the bolt is not even moving, slight bounce after the shot, then I think you're missing the gas. if you're getting some gas, the bolt should bounce a little, and if it doesn't come back far enough to kick the spent case out the side, might slam it back into the chamber. but if the bolt bounced a little, it would've broken loose the iron grip and it'd be easier to manually extract.

after the 7.62x39 round is fired, the steel case expands to the chamber and is by itself, difficult to extract. I made the mistake of putting a fired case into the chamber and sending the bolt home. had a hell of a time yanking the charging handle to get that one out, mortar. dumb idea, lesson learned. and that was on a perfectly fine functioning 7.62x39 upper.

 

[flynlow3]

Gas tube is installed correctly. Double checked it. I also tried firing with no mag. Same issue so it's not a magazine problem. I wonder if the chamber isn't cut properly? Headspace issue. Could the bolt be locking in place from that?

Running out of ideas

Thanks

 

[sam4886]

Sounds like a rough chamber coupled with the steel cases expanding and sticking. You may be able to turn the gas up or drop spring/buffer weight and over power the sticky shit.

I have an AK, so I know its not real easy right now, but you should try some brass cased stuff if you can find it.

If it were mine, I would polish the hell out of the chamber. It's a 7.62, you're not going to ruin accuracy.

 

[iktomi]

What info do you have on the upper?

Do you have access to micrometers? (Your cases might be blowing out from a large chamber not offering support to the case.)

What info do you have on the BCG / Buffer / Spring rates?

Extraction is a combination of force and timing. Changing one will not necessarily correct for the other.

Brass and steel cases have fundamentally different mechanical characteristics.

If you're shooting steel, there are a number of other potential issues that need to be considered (e.g. over expansion / lack of rebound / case blow out, lacquer / coating transfer to the chamber) that are not present when shooting brass cases.

 

[bfoosh006]

Can you post some pics of the fired cases, looking for scuff marks and such... anything that might be caused by a rough chamber.

 

[db2000]

They’re $260 at Bear Creek Arsenal. Just buy another. Mine runs flawlessly. A friend has a midway AR Stoner brand and works fine too. Paid $560 for his though.

 

[supercorndogs]

"Works flawlessly until its fired."

That is the most round about way of saying it doesn't work worth a shit, I have ever heard.

 

[hlee]

Yeah, a better description might be “manually cycling the rifle fails to identify a problem…”

 

[MadDuner]

Are the rings intact on the bolt when you disassemble the BCG?

 

[flynlow3]

Had multiple issues. Cotter pin that holds the firing pin was not seated properly through the bolt and was rubbing inside the upper. Cotter pin was bent inside because whoever assembled the bcg missed the hole and just sent it.. Chamber was rough and gas port was undersized. The firing pin spring was increased because it wasn't igniting the wolf ammo. Lots of light primer strikes. Magazines had slight mods for better feeding. All runs good now. Lesson: buy cheap shit and it's like an adult puzzle to fix it.

 

[Dank27]

Mine had a bad gas block and needed the BRA firing pin but since fixing thos items it shoots great with all kinds of crap ammo.