7.62x25 chamber problem, need opinions.

[garagegunmaker]

Looking for opinions on this…

Just picked up a pps-43c new. Had some polish surplus ammo I had planned to run in it, 53 headstamp date.

Loaded up a mag and fired, first three rounds with no issues at all. Then on round four just a click, with the slightest hint of a mark on the primer. I know the surplus polish ammo is known for hard primers so I was not surprised.

Tried to extract the round and found the the extractor would not grab the case, so used the tip of my knife to get it out.

Tried a new round and same problem…10 new round in a row and not a single fire, and almost no mark on the primer.

At that point I was getting fed up with pulling rounds out with the knife, and figured I would rule out ammo. Fired all 10 round that had not gone off thru a cz-52, all 10 fired in the first strike.

I was Assuming maybe defective or broken firing pin on the Pps at that point. Took it apart and didn’t see anything wrong with it, except seeming slightly short. Have read they were designed with commercial ammo in mind and not piercing primers though.

Figured I would try some new commercial ammo next to see if it functioned with that, and sure enough it fired 10 round no problem.

Still had the same issue when I went to unload that the extractor would not grab the case.

Figured I would make an extra firing pin a few thousandths longer and swap it in then shooting surplus, and problem solved…till I noticed the spent casings from the commercial ammo.

They look very stretched and neck misshaped. Almost like the chamber is cut to deep or incorrectly? Got me thinking about the extraction problem, which could be related to chamber depth.

Also could that be causing the issues with the surplus ammo not getting enough hit from the firing pin, but then why did the first 3 rounds fire with no issues?

Sorry for the long post, just looking for others opinions on this. Hate to send back a new gun for warranty work, especially if it’s something simple I could fix myself.

Here is a picture of the fired brass next to the same ammo unfired.

Any thoughts are appreciated, thanks!

 

[edwea]

9mm barrel perhaps?

 

[DoggyDaddy]

9mm barrel perhaps?

They did make those PPS-43's in 9mm, so that might be a good bet. Should be able to tell right away by inserting a 7.62x25 round into the muzzle. Although the gun should be marked as to caliber as well.

 

[russc2542]

That's some serious shoulder stretching! I agree with doggydaddy, plunk test it at the muzzle. (I just checked and a x25 will plunk and chamber in my 9mm CZ52 so that's not decisive)

They did make those PPS-43's in 9mm, so that might be a good bet. Should be able to tell right away by inserting a 7.62x25 round into the muzzle. Although the gun should be marked as to caliber as well.

*Should* but with surplus stuff and who knows how many home 'smiths hands in it you never know. I have a CZ52 with a 9mm barrel with only the barest hint of a stamp "9mm".

 

[DoggyDaddy]

(I just checked and a x25 will plunk and chamber in my 9mm CZ52 so that's not decisive)

My thinking was that the x25 will probably go in right up to the brass (when inserted bullet first) at the muzzle end. If it doesn't, then it is probably not a 9mm barrel/chamber.

 

[russc2542]

My thinking was that the x25 will probably go in right up to the brass (when inserted bullet first) at the muzzle end. If it doesn't, then it is probably not a 9mm barrel/chamber.

yes, if the muzzle eats it up to the shoulder, it's a 9mm barrel. If it stops on the bullet/case mouth it's 7.62.

 

[garagegunmaker]

Thank you for all the replies so far.

I had had the thought about the 9 mm barrel or chamber should have mentioned that in my first post.

Here are pictures of the round chambered, bolt interface, and barrel end which all appear to be correct. Round will not go any deeper in the chamber than shown in the picture which seems correct.

Looking down in the chamber with a light I see a definitive shoulder cut that appears clean.

Any other thoughts on what would cause the case stretching?

 

[garagegunmaker]

Tried my best to get a picture of the chamber.

 

[DoggyDaddy]

Thank you for all the replies so far.

I had had the thought about the 9 mm barrel or chamber should have mentioned that in my first post.

Here are pictures of the round chambered, bolt interface, and barrel end which all appear to be correct. Round will not go any deeper in the chamber than shown in the picture which seems correct.

Looking down in the chamber with a light I see a definitive shoulder cut that appears clean.

Any other thoughts on what would cause the case stretching?

That's a stumper for sure. Other than having a gunsmith do a chamber casting, I'm at a loss.

 

[garagegunmaker]

What is the method for doing a chamber casting? Probably something I could do myself

 

[DoggyDaddy]

What is the method for doing a chamber casting? Probably something I could do myself

That I don't know, but there are probably youtube videos on how to do it I'm guessing.

 

[garagegunmaker]

Ok I’ll look into it, never hurts to learn a new skill.

Had another thought, being direct blowback would the case deform that bad from either a worn out recoil spring or too little bolt mass. Making the bolt move rearward too soon and the case moving back with it, and deforming as it is still under pressure.

Most direct blow backs are with cases that don’t have a neck, so it would not be noticed if it was happing with them.

Thoughts?

 

[garagegunmaker]

They do lighten the bolt when they convert the parts kits to semi auto by grinding off the sear notch, milling a groove for blocking bar of auto bolt, and drilling out for a firing pin vs fixed pin from open bolt.

 

[russc2542]

Lightened bolt assembly/underpower recoil spring in a straight blowback could conceivably do it, yes. Bolt's opening early so there's enough pressure to fireform the neck with the case partially removed AND the case is a bit soft/wiggly allowing the extractor to lose grip since there's more friction than it's designed for due to the increased pressure.

 

[Leadeye]

From the looks of the fired case you need to get some Cerrosafe and do a chamber cast. Not hard to do and instructions come with the stuff when you buy it. Follow them exactly paying attention to the times involved. Guessing, I would say the chamber was cut too deep.

7.62X25 is one of those cartridges that I've seen a lot of variation in neck length and shoulder angle having shot a lot of Broomhandles. Ammo usually has a longer neck and a lower angle going in and a shorter neck with a sharper angle coming out after firing. It's also an issue with some 38-40s.

Your fired brass looks like it is head spacing on the case mouth rather than the shoulder, and then the shoulder is blowing out when fired.

 

[DadSmith]

Looking for opinions on this…

Just picked up a pps-43c new. Had some polish surplus ammo I had planned to run in it, 53 headstamp date.

Loaded up a mag and fired, first three rounds with no issues at all. Then on round four just a click, with the slightest hint of a mark on the primer. I know the surplus polish ammo is known for hard primers so I was not surprised.

Tried to extract the round and found the the extractor would not grab the case, so used the tip of my knife to get it out.

Tried a new round and same problem…10 new round in a row and not a single fire, and almost no mark on the primer.

At that point I was getting fed up with pulling rounds out with the knife, and figured I would rule out ammo. Fired all 10 round that had not gone off thru a cz-52, all 10 fired in the first strike.

I was Assuming maybe defective or broken firing pin on the Pps at that point. Took it apart and didn’t see anything wrong with it, except seeming slightly short. Have read they were designed with commercial ammo in mind and not piercing primers though.

Figured I would try some new commercial ammo next to see if it functioned with that, and sure enough it fired 10 round no problem.

Still had the same issue when I went to unload that the extractor would not grab the case.

Figured I would make an extra firing pin a few thousandths longer and swap it in then shooting surplus, and problem solved…till I noticed the spent casings from the commercial ammo.

They look very stretched and neck misshaped. Almost like the chamber is cut to deep or incorrectly? Got me thinking about the extraction problem, which could be related to chamber depth.

Also could that be causing the issues with the surplus ammo not getting enough hit from the firing pin, but then why did the first 3 rounds fire with no issues?

Sorry for the long post, just looking for others opinions on this. Hate to send back a new gun for warranty work, especially if it’s something simple I could fix myself.

Here is a picture of the fired brass next to the same ammo unfired.

Any thoughts are appreciated, thanks!

Have you called the manufacturer and ask them? Maybe send it to them to check it out?

 

[55fairlane]

Cast the chamber.....a set of go/no go gauges will help tell the story, but I am inclined to believe either the chamber is cut way to deap or the chamber is not 7.62x25 , either way your gun has issues and unless the manufacturer warranties the gun, plan on a new barrel.