Premature Firing?

[Blueliner]

I took my P64 to the range for the first time yesterday and there was an issue. It was during my 5th magazine and nothing unusual had occurred to that point. Then…
Upon firing, there was a smaller than normal bang, a flash of light came out of the right side of the weapon, a fragment (part of the brass case) hit my forehead as well as another on my glasses. My hands received a lot of gunpowder residue. The bullet exited the barrel and actually hit the paper. The fired casing was mutilated (see picture as shown in chamber) and was lodged near the chamber. The round below it in the mag attempted to load and mashed the spent casing upward. It was stuck pretty good and the mag would not eject. I popped the slide off and was able to free the problem and eject the magazine. The non-fired round was shorter by 3mm as the bullet impacted into the brass by that much.
One of the range owners is very knowledgeable and curious and wanted to examine it. It appears the round fired a bit early and the exposed part of the case exploded out the side (see picture) like so. He surmised that perhaps the firing pin spring was weak and did not return
Here is what I can tell you for sure:
Upon receipt of the P64, I did the following:
1. Soaked it overnight in mineral spirits
2. Blew it off with compressed air
3. Slathered it with wd-40
4. Blew it off with compressed air even more
5. Replaced the slide spring (Wolfe- standard spring)
6. Replaced the Hammer spring (Wolfe 18lbs)
7. Oiled the firearm
8. Reassembled it
9. Tested its operation in its entirety except firing it.
It is in exceptional shape and as close as I can tell may never have been fired.
I was using PPU ammo with brass cases, 85gr FMJ
It fired small groupings and operated perfectly to that point.
In my short time on this forum, I have been impressed with the knowledge here and am hopeful that someone(s) can educate me further about what might have happened and how to fix it.

[juniustaylor]

I'm glad you're okay! I am not convinced it was necessarily the gun's fault. There are numerous times on this forum where folks have showed pictures of their Prvi Partizan (PPU) brass. There are bulges at the case web area from where it is unsupported at the bottom of the chamber. I wonder if your issue has to do with the web of the case blowing out at the same time the slide was going to retract. So, it would make it look like the gun fired prematurely.

Think about it. Correct me if I am wrong... The gun did NOT go off until you pulled the trigger? If that is true, then it wasn't a case of a "slam fire" at the fault of the slide. Also, the gun should not go off unless it is fully into battery. If you pulled the trigger and it for some reason went off without being all the way locked in, then there is an issue with the gun there, but I highly doubt that is the issue.

In my opinion (FWIW) I think it was a case of crappy ammo. The webs on these PPU brass is weak. You can shoot steel case and reloads made from 9mm Luger brass all day long and you shouldn't end up with bulged cases as these PPU brass exhibit.

Hopefully some other members will comment as well.

[juniustaylor]

viewtopic.php?f=1&t=4599

[Blueliner]

Failure of the case was the other option we considered at the time and when it occurred is the only thing I thought it might be.

You are correct, it fired after I pulled the trigger. What you say has given me cause to really consider this... It happened very quickly so I may not be accurate in what happened but at the moment it happened, I thought the explosion out the side happened just a tick after the expected boom. Sort of like BOOM...fizzle. Looking at where the case fractured, and where that spot is located in the chamber, logic tells me you are absolutely correct. Thank you for the opinion.

Unless someone comes up with a good alternative I am going to go with that answer. However, since I have firing pin springs already, it can't hurt to replace those as well.

[juniustaylor]

If you've got the firing pin spring, I'd probably change it out anyway. It never hurts and it's just added peace of mind.

[Blueliner]

That is exactly what they described and where this round blew out is where the notch is. Thanks so much for the linky. I am going to get some steel case for the P64 and use the PPU in my CZ82 which has more support down there. Lesson learned... The funny thing it that I bought a bunch of PPU because it has a brass case so that I could take it shooting at a range my friend is a member of. A range that does not allow steel CASES. The range I belong to allows steel cases.

re: firing pin spring- yup, I'll do that. I like to see how stuff goes together anyway.

[Curly1]

A good reason to always wear safety glasses, glad there were no injuries.

I agree with Junius, ammo casing failure and change out the firing pin spring to be sure.

I always squirt some solvent with a spray can with plastic straw placed up against the firing pin in the slide face followed up with some compressd air to flush out any junk thru the back of the slide after shooting any of my guns. Repeat until clean fluid comes out.

[Blueliner]

Sounds like a winner Curly. Thanks for the tip.