Ouch! Be Careful Out There

[alfsauve]

Had a case head blow out today.  Second shot of a local match.  Darn.  Took the extractor along with it.  My Sig P320.

1)  Double Charge:  Unlikely as the charge fills the case by half.
2)  Detonation:  Remote, though I am running at the suggested low-end charge.
3)  Case Head fault:  I think most likely. 

The data:  3.2gr TiteGroup, mixed lot cases, Fed 100 Primer, Xtreme 147gr Plated, 1.12" COL.

The slide cycled, though I can't remember whether it felt unusual.  Blowback in the face and on the strong hand.  Extractor broke off and hit the trigger finger.  Small welt.  Can't find the extractor.  Went to an unused range and fired another round.  No problem other than FTE.  Barrel, FCG, frame and slide all look okay.

Oh, and that round scored -0 with a clean hole and no shrapnel in the target.  SO didn't get hit with any blow back.

[Marshal Halloway]

Oops....

Glad you're ok.

[Rastus]

Ouch and wow. 

I would think if you had a detonation you would have felt additional recoil.  Detonations can be more violent than normal explosions.  I worried about that in hydrocarbon piping whenever we opened up for maintenance. 

[MikeBjerum]

Looks like the something caused it to fire before it was in battery.

Is it possible something happened during the first round that caused the striker to hang up? That would cause a slam fire situation, and the primer got enough pressure to detonate while still not in the chamber.

[PegLeg45]

Looks like the something caused it to fire before it was in battery.

Is it possible something happened during the first round that caused the striker to hang up? That would cause a slam fire situation, and the primer got enough pressure to detonate while still not in the chamber.

That's the first thing I thought when looking at the photo. That much damage in that area looks like unsupported surface eruption. I've seen it in those "Perfected Pistols" but don't know about the Sig guns as I do not own any.

[Sponsor]

[Majer]

I was going to say out of battery discharge from the looks of the case(What's left of it) Most likely an out of spec case didn't allow it to go fully into battery.

[Rastus]

Good insight followups guys!!

Nice to see you around Marshal!

[Big Frank]

Wow. I've never seen a blowout like that before. I'm glad you're okay Alf. I only had a case head blow out once, and that was on a .22 LR. It was just a piece of the rim, and the rest of the case was fully supported in the chamber. It blew the extractor and related parts out of my 10/22, but it still worked most of the time while I finished that mag, or that box full of ammo. I can't recall now which it was, but the cases blew back into the ejector and out of the gun the  majority of the time. Like Mike said, that looks like it fired out of battery. My guess is the case was oriented the opposite way, and the big gaping hole is what caused the extractor to blow out of the gun.

[alfsauve]

Actually the blow out was downward.  The picture below I've put the case back in the barrel and it only fits one way, since it's been "fire formed".  For those curious it was an S&B brass "22" or "21" marking.  Year of manufacture?  And I chamber check all cases after sizing and again after I finish loading. 

The very top of the head is not supported in Sig nor Glock.  Even it it was there has to be space for the extractor so some portion would be unsupported.  Even revolvers don't have fully supported heads if they use moon clips. 

It was a purposeful shot, for those suggesting the P320 fired on it's own.  I aimed and pulled the trigger.  (Down Zero/bullseye shot)  I've had other guns go double on me so I know what that feels like.

I'll play with it and my feeler gauge but I don't think out of battery was the issue.   

ON SIG EXTRACTORS.  I had assumed, like a number of guns the extractor pivoted on a pin.  I've never paid much attention to how the SIG works.  Turns out they free float in their slot and are held in place buy a pin that slides longitudinally pushing on the rear section of the extractor..  Unlike, say an AR extractor, this one is U shaped.   Makes it very easy for them to blow out, like this one did, with out shearing anything.  Had I known I'd spent more time searching for the missing piece.

I've replaced the extractor and run tests with dummy rounds all seems to work fine.  Am going to the range shortly to live fire it.

[PegLeg45]

Could've just been a "tired old" case or weak spot where the case was formed.

I saw that once with a low pressure .45 ACP round. The case ruptured and blew down the magwell and split the left grip panel.