What causes these blowout shells?
M1A shooting all of them.
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Is there a hole in the chamber? Should be able to see that.
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Brittle brass, over pressure maybe, flawed brass from the factory or an extremely over sized chamber coupled with brittle brass.
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Overworked brass, stretching causing a thinning of the brass in the web area above the base. When sizing, bumping the shoulder to far back can cause the brass to flow forward when the cartridge is fired. This can also cause case separation. From the looks of those, it's time to visit the auction side for some new brass. Bob
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None of the above.
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bpost: 30055622133019/comments/30055634789659
Brittle brass, over pressure maybe, flawed brass from the factory or an extremely over sized chamber coupled with brittle brass.
Yep, seen before with Milsurp.
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I'll take a "shot" at it.🙄
I would think that there's a good possibility of age-hardening/embridlement of the brass......depending on the brass storage temperature swings over it's lifetime.
Also......all of the incipient casehead separations/cracks I've seen, or had, have been circular(around the case body), at about the case web datum point.
Hope this helps.
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Oversized/headspace case fractures are annular, running parallel to the case head. I can't think of a cause that would consistently produce a longitudinal crack like those. Have to ponder that a bit.
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The only instance of this I've seen involved some military brass that had been originally fired in a grossly oversized chamber and then reloaded. A tiny flaw or something caused the brass to expand more in a small area leaving a weak spot that blew out upon firing the reloaded round.
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Being that the brass is no longer usable, I would take one of the cases and cut it in half just above the split. Then clean the case out in order to get a better look at where it split. This would maybe rule out if the brass has been over worked in the past.
This is assuming now that this is reloaded ammo.
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/Sarc on/ Aw, heck. Those can be fixed right up with a little brazing rod and judicious file work. /Sarc off/
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I vote for defective brass. Defective from the get-go. We don't have a lot of information, just the picture. The OP did not indicate whether reloads or factory. I'll bet they were original, perhaps military cartridges. "Inclusions" in the brass before the draw. I used to work in quality control for a factory that made brass parts on multiple spindle bar stock machines and we would get an occasional brass bar with an inclusion that, after the draw, would cause a weak line that ran most or all of the 12 foot length of the bar. Parts made from that bar would crack.
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My dad was a big garage sale guy. He bought me some .270 rounds winchester or super x in the yellow box. They were probably 30 years old but not reloads, factory stuff. Almost all of them blew out like that.
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It is the case at fault, not the firearm.
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My first vote is incorrect, excessive headspace
my second vote is excessively annealed cases
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Yes, you are correct. It was old military surplus. Perhaps 30 year old.
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kannoneer: 30055622133019/comments/30055646621723
It is the case at fault, not the firearm.
Agree, reading the OP, the rifle firing was an M1A. M1As may have issues but headspace is not one of them providing the barrel was installed by SA.
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Upon cogitation and reading the replies, I agree that it was likely brittle brass. Milsurp ammo might not be up to the quality of commercial cases, and brass can embrittle with age.
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