Chamber erosion

[1911Prof]

I have a PSA 9mm carbine with a couple of thousand rounds flawlessly through it and started having a problem extracting the unfired cartridge from the chamber when I was finished shooting.  The extractor hook was not gripping the rim so it would leave the cartridge in the chamber.  I inspected the extractor and it appears fine.  Then I started getting light strikes (barely a scratch on the primer) so I pulled the barrel and noticed that a cartridge will sit about .030" deeper in the chamber compared to a different barrel.  When I put the bolt up against the barrel face, the bullet is not flush against the breech face such that the extractor hook does not engage the rim.  So I am assuming that the chamber has eroded enough to cause these problems. Is this typical?

Edited April 2, 2018 by 1911Prof

[MikieM]

Sounds like you know what the problem is, but not quite what caused it. I wouldn't call it typical that's for sure.

The cartridge sits deeper in the chamber now, correct? Can you shine a small bright light down he chamber and see if the ledge the cartridge headspaces on has changed in any way?

At any rate a new barrel may be in the offing.

[1911Prof]

I really can’t see any visible signs of wear on the ledge on the headspace and I would suspect ammo but the same cartridge definitely chambers different in two barrels from the same manufacturer.  I guess I want to know if there is something that I should be avoiding 

[MikieM]

10 minutes ago, 1911Prof said:

I really can’t see any visible signs of wear on the ledge on the headspace and I would suspect ammo but the same cartridge definitely chambers different in two barrels from the same manufacturer.  I guess I want to know if there is something that I should be avoiding 

 

If you can get one, try chambering a factory round.

[Xanatos903]

Like Mikie said, this definitely isn't typical, especially over only a few thousand rounds. You really don't see erosion of the shelf for the case mouth, and the only way throat erosion would change how deeply the bullet sits in the chamber is if the bullet was jamming into the lands, as opposed to headspacing on the mouth of the case.  

 

By any chance, do the different barrels have different looking feedramps? I know that my rounds look different when plunked in Glock vs 1911 barrels, for instance. 

 

In all, it sounds to me like you have problems with your loading process. Does this same round that looks like it headspaces oddly pass your case gauge with flying colors?

Edited April 2, 2018 by Xanatos903

[L9X25]

More than likely your barrel was chambered a little deep from the factory and you have been using the extractor to provide the head-space and it has worn from the effort.

 

If the ledge at the end of the chamber is still sharp and square, it is not erosion.  Assuming it is just a deep chamber, you could pull the barrel and surface the face to effectively reduce the chamber depth.  Then you could replicate the bevel that came from the factory and it will be fixed.  You will likely need to replace that extractor too.  

 

ETA: I had a barrel that came that way too, but I found the problem before firing it.  A sharp extractor with good tension can extract an unfired round without getting into the extraction groove.  Once the sharp edge smooths out, or it loses a little tension, it will slip more often.

 

Edited April 2, 2018 by L9X25

[rishii]

I had the similar problems with my psa, I never checked how far the ammo sat in the chamber like you did

after a few range trips I finally figured it out

the roll pin holding the extractor in place got bent, which allowed the extractor to move back and forth in the extractor tunnel 

when it was forward, it operated normally 

when it was back, the extractor would not slip over the extractor groove and hold the bolt a nats ass out of battery resulting in light strikes and failure to extract