I recently had a strange case failure that I haven't seen in my 20 plus years of loading my own. The entire joint of the case wall and head cracked and the extractor groove was shoved into the case.  The round fired and functioned fine and I didn't even notice there was a problem until I was resizing brass and one wouldn't fit into my shell holder. Like I said I have never seen this before and was wondering if anyone else has.

Sorry for the crappy iPhone pictures

Here you can see that almost the entire circumference fractured.


Here you can see how much the extractor groove and case shortened when the case head was shoved into the case.

Few questions...
What was the casing manufacture?
Was it fired in a Delta or unsupported 1911 style barrel?
What was the loading? Handload? Factory?
If handload what was used? Powder type? Charge weight? Bullet weight"

It is from my standard plinking load. Winchester brass, Winchester primers,5.5grs Titegroup under my 180gr powdercoated bullets. Fired from my stock gen4 Glock 20.

That is weird...Do you know how many firings on the case? 
Where they range pick up? or originally new to you?
Where they cleaned in liquid solution?

They have the signature Glock bulge.

There is pressure for sure.  Too much pressure.  You do need to find out what caused it BEFORE you use the gun again. 

Is the barrel leaded?

Is the bullet able to be set back during the process of being stripped from the magazine?  (PPU brass?)

Could it have been a double charge?

That baby is almost a case head separation.  I've never seen one like that.  Interesting!!!  It shows the intermediate step just before letting go.  That would likely have been a new Glock frame, magazine, and you would be out $100 plus the hassle of shipping a firearm next day if it had gone any farther.

Greg

According to Quickload, 11 grains of tight group is a 105% compressed charge (not hard to seat the bullet) and pressure of 120k PSI.  Quick load isn't so good with pistol loads, and it tends to over estimate pressures. 

If the bullet was able to be set back until the bullet hit the powder (100% fill) with 5.5 grains, the pressure is estimated to be in the 73k PSI area.

Both are possibilities.

Greg

Maybe you accidently overcharged the powder in that case? A couple months ago, my RCBS Chargemaster quickly dispensed 8.2 grains of Longshot into one of my cases. I should say, it too quickly dispensed 8.2 grains of Longshot. So, just to be safe, I set the charged case aside to reverify it at the end of the powder charging session. I also visually inspect all powder charged cases in the loading block to make sure it doesn't look like any received some additional powder.

The suspect case received a charge weight of 11.2 grains of Longshot despite what the Chargemaster originally displayed. If I hadn't been paying attention to the unusual speed at which the RCBS filled that particular case, things could have been bad.

Maybe something similar happened to you.       

Case head separation that the gun's action reassembled for you.

Quote from: Benchrst on December 18 2015 06:43:23 AM MST
Case head separation that the gun's action reassembled for you.

We have a winner.  I bet the shot was a bit funny too in sound or recoil, but not enough that it stood out to you.

If you look closely at the case that didn't separate it looks to have a cut groove deeper than it should be, or it too was being separated as well...The loading as listed 5.5grs Titegroup under my 180gr powder coated bullets, would be OK.  However it could be a double charged or partially over charged situation. (things like powder bridging also come to mind)

Definitely warrants a closer look at things.

That could have been disastrous. Glad you weren't hurt.

Quote from: Captain O on December 18 2015 10:07:33 AM MST
That could have been disastrous. Glad you weren't hurt.

Another winner, whose sentiments I echo!

I have a question for you all. The more I think about it the more I think my case sizer is squeezing my brass too much. The above post about  both cases having "Glock bulge" made me look at my resized cases a little closer. In the pic above there is no case bulge on the case to the left. It has been sized and the case wall actually is narrower than the case head. It appears as a bulge in the pic but in fact it is not. I wonder if working the brass too much over a few loadings could have caused the case failure like I had?

Quote from: Pumpkinheaver on December 18 2015 03:11:46 PM MST
I have a question for you all. The more I think about it the more I think my case sizer is squeezing my brass too much. The above post about  both cases having "Glock bulge" made me look at my resized cases a little closer. In the pic above there is no case bulge on the case to the left. It has been sized and the case wall actually is narrower than the case head. It appears as a bulge in the pic but in fact it is not. I wonder if working the brass too much over a few loadings could have caused the case failure like I had?

What do your calipers say?

That case on the left defiantly looks bulged.  My resized cases look nothing like that.

Jeff