I'd guess case failure, the case head separated from the case and dumped hot pressurized gas in the breach area and that blew out the magazine. If the charge weight was 4.5 gr of W231, no way is 9 gr of powder going to fit a 9mm case without spilling everywhere and being VERY noticeable.
ETA: if the round went off out of battery, that could also cause a case head to let go the way OP pic shows.
I had a case head separation happen with an AR once, and it left a perfect brass tube stuck in the chamber. Blew out the mag, mangled my extractor. IIRC, the bolt was otherwise fine.
ETA: if the round went off out of battery, that could also cause a case head to let go the way OP pic shows.
I had a case head separation happen with an AR once, and it left a perfect brass tube stuck in the chamber. Blew out the mag, mangled my extractor. IIRC, the bolt was otherwise fine.
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