I don't know what it is about us but I've seen some of the weirdest scenarios show up on this reloading forum and this one's right up there with the most bizarre of them. We need Rod Serling and his team to investigate this one. I can hear the music now.
Old funky deteriorating powder is what I'll put my money on. It just sat there and got hot instead of building up pressure; but we'll never know for sure.

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Where we go one, we go all