I'm betting that cartridge had its bullet seated way too far out and it jammed solidly into the leade when he tried to chamber it. Most likely cause: inadvertently short stroking the press handle. The fact that he couldn't subsequently eject the cartridge says that bullet fit in those cartridges was/is pretty darn tight, so crimping would've been superfluous (and would be in future with the same lot of brass/bullets). Normally in a situation like that the bullet stays put- jammed into the leade- and the case pulls away from it when ejection is attempted, unless like now it was inordinately tight in the case neck.
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While I know this can happen, I don't think it happened in this case. If the bullet was stuck in the lands and the bolt was open, hammering it out wouldn't have pressed the bullet into the case. Seems like the case itself was wedge in the chamber somehow with the bullet free and able to move.
It would seem you guys experienced a perfect storm of small things that added up to a catastrophe. Just what each of those small things were remain a mystery.
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Agreed. We'll probably never know.
