What caused this

[bigedp51]

This photo was posted in another forum, would using too slow a powder and high port pressure cause the case to balloon on extraction. And if it were a out of battery firing wouldn't the base of the case have ruptured? I have never seen anything like this before and have been reloading for over 47 years.



Can you see me now?

[gaijin]

I see no photo and need additional info; what firearm used, bullet, case, powder and charge?

[Ned Christiansen]

Gonna guess it's a bulged .223.... they "look" like it must have been out of battery when it bulged but really they're just bulging into normally-occurring, available space, that being the chamfer at the back of the chamber and the chamfer at the mouth of the bolt face recess. If I'm right, what you have is a round that was over pressure for some reason and the gun was within half a PSI of getting blown up.

[markm]

With no pic, I'm also guessing .223. I've only seen bulging on my Wylde chamber with hotter loads of .223.

[thopkins22]

I can’t see the photo on my iPad, but things have to be really out of spec to fire out of battery. Like really out of spec to the point that even when all the evidence points to that happening I’d still be skeptical and look for something else that could have happened...likely what Ned suggested.

[Ned Christiansen]

Hm. Look how short the necks are. The dimension from the base to the top of the bulge is longer than expected, longer than the distance from the bolt face to the end of the chemfer lead-in to the chamber (unless it's way, way deep. Those short necks are telling us something, just not sure what, yet.....

Has this gun been fired before successfully, has anything recently been changed (bolt, barrel), any chance this is .222 ammo?

Maybe the necks are getting short because the brass to make that bulge hadda come from somewhere. In which case.... looking at that lead-in chamfer again.

[Clint]

Ned,

I think you're on to something.

My first thought is something like massive excess head space to explain the short necks, but the improper chamber mouth seems to fit too.

Hm. Look how short the necks are. The dimension from the base to the top of the bulge is longer than expected, longer than the distance from the bolt face to the end of the chemfer lead-in to the chamber (unless it's way, way deep. Those short necks are telling us something, just not sure what, yet.....

Has this gun been fired before successfully, has anything recently been changed (bolt, barrel), any chance this is .222 ammo?

Maybe the necks are getting short because the brass to make that bulge hadda come from somewhere. In which case.... looking at that lead-in chamfer again.

[markm]

Oh Lord. That's way more bulging than I expected to see. Going to definitely need a small base die to resize!

[Ned Christiansen]

If they were .222 or something they ought not to fire as they would be kicked too far forward upon chambering. I saw this just a month ago when a Dept. was having misfires with some commercial reloads. The necks were verrry long-- rounds were not being "stopped" by the shoulder, so the extractor could not clip over the rim and the firing pin could not reach. Some did work so they were borderline.

I think it's the chamber mouth chamfer. Can we get a pic of it?

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I just re-read the OP and I see we are dealing with something a place or two removed from "it happened to me". This reminds me that anything can happen when people start improving things and unless we can get closer to the situation I wonder if it even merits further discussion. Not casting aspersions on you OP, it's an interesting ocurrence, but can you bring this any closer?

[Bimmer]

Hm. Look how short the necks are...

Maybe the necks are getting short because the brass to make that bulge hadda come from somewhere

I don't think it's that the brass from the necks wound up in the bulge.

I think it's that the whole case is ballooned, which pushed the shoulder waaaay forward — think of how wildcatters "improve" cartridge cases.