Head case separation

[optimumdetails]

Saw this with ****ty brass before. Not sure if it is properly sized or length is too long but some rounds wouldnt properly seat. They were close enough to allow primer to be struck but not lock the bolt in battery. The result blew the side of the gun out. You can see in the pics how some rounds would chamber properly and some wouldn't. Luckily nobody was injured.

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[T-Roy]

You have obvious bulging after the ejection cycle has started.

Flashover can happen when the powder load burns across the top of a light load as opposed to an end to end burn pushing the projectile out the tube. A primer alone can drive a bullet into a barrel. What happens if that primer strike starts the cycle and the flash happens a tad later than it should?

When I reloaded I would carefully measure the space involved and I tended to use bulkier powders just for that reason.

Okay. That makes a lot of sense.

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[T-Roy]

Saw this with ****ty brass before. Not sure if it is properly sized or length is too long but some rounds wouldnt properly seat. They were close enough to allow primer to be struck but not lock the bolt in battery. The result blew the side of the gun out. You can see in the pics how some rounds would chamber properly and some wouldn't. Luckily nobody was injured.

Sent from my SM-G960U using Tapatalk

My m&p held up better than that keltec, fortunately. However some of the small parts in the sear block didn't survive. Having to replace the sear block assembly. Bent the slide release detent. Also replacing the extractor because I can't imagine there's not potential damage. One magazine butt plate isn't flat now.

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[T-Roy]

Just a thought, I think you are firing out of battery. Reloaded a lot of hot and mild shells and never seen this with a light load.
Your primer shows over pressure big time. If you loaded lite, out of battery would look like those.
I would resize, measure case length, reinspect and load another at your lite load. Do a plunk test to make sure you are all the way in the chamber.
Then set up a jig to test fire. I think when you did not resize that caused the problem? Just a dumb thought that’s not a 9x23 case?
I think I would also inspect your pistol.

Had the same thought and tried a few rounds in my ar9. Blew one within the first 3. So i feel like it's the ammo.

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[1006]

Just as a double check of your loads:

check the powder measure drop for 3.7, and the bullets to make certain they are 115g.

If the powder is 20 years old, it may have changed, but not very likely.

A blowout has to be extreme to damage the gun, a weak brass blowout of a standard load will not damage the gun; good manufacturers engineer that safety into the gun. They know these things happen. I had one with 9 major in a Glock, it simply failed to cycle the gun.

 

[T-Roy]

The powder is a couple of years old, got it from a friend (that I trust) and the data is current from the manufacturer.

After reading all of the smarter than me comments on here and pulling out the pistol I've come up with a new theory.

Currently there's something bent/broken that will allow the gun to fire before it's locked. I think there was some damage from the overcharged loads 2 weeks ago that I missed and maybe this weekend I had one go off out of battery.

The hot loads had more force by far, but it was the lighter load that damaged the mag and dislodged the backstrap.

The pic shows where the slide and barrel sit when the trigger bar engages vs. fully locked. That ain't right. It's a frame issue, been doing some slide swapping this am.

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[DanKATL]

The powder is a couple of years old, got it from a friend (that I trust) and the data is current from the manufacturer.

After reading all of the smarter than me comments on here and pulling out the pistol I've come up with a new theory.

Currently there's something bent/broken that will allow the gun to fire before it's locked. I think there was some damage from the overcharged loads 2 weeks ago that I missed and maybe this weekend I had one go off out of battery.

The hot loads had more force by far, but it was the lighter load that damaged the mag and dislodged the backstrap.

The pic shows where the slide and barrel sit when the trigger bar engages vs. fully locked. That ain't right. It's a frame issue, been doing some slide swapping this am.

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Do you have the factory M&P barrel to compare chamber support? Those casings look like they were shot in an unsupported chamber (sometime called glock bulge) and then fixed with a bulge buster die. If the former bulge just happens to line back up where it's not fully supported, you have a higher chance of a blowout. That chance is higher if they were loaded hot.

 

[T-Roy]

Do you have the factory M&P barrel to compare chamber support? Those casings look like they were shot in an unsupported chamber (sometime called glock bulge) and then fixed with a bulge buster die. If the former bulge just happens to line back up where it's not fully supported, you have a higher chance of a blowout. That chance is higher if they were loaded hot.

The misfires actually occured in a factory barrel. That's the slide off a different gun. Took the pics when I was comparing where the trigger engages and swapping slides. Result was the same with both slides

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[Greybeard]

I think you found the problem with the pistol, that slide looks like it is not locked.
For you ammo, I think I would pull all and discard all the brass and powder. I think (just me) I would switch powder to w231 (Hp38) or unique. I don’t think your powder would be bad, but I would start with different brand. As suggested reweigh and measure your bullets and measure your new brass. Then again once resized and when reloaded your oal.
once you establish a good starting point you can then eliminate your loaded bullets and look elsewhere if it happens again.

 

[Freshly Minted Georgian!]

Old timer trick, take a sized case and confirm the proper OAL. If the length is OK take a fine dental pick and stick it inside the case putting the tip against the case wall right where it intersects with the base. From there slide it up the inner wall of the case. You can actually feel stress rings (if they exist). Because the outside of the wall will be straight from your sizing die if the case has been abused and thinned down towards the base it'll show up internally as a thin ring you can pretty readily feel.