Jonesy,
My reading on the subject of detonation suggested that it occurred in large capacity cases, like rifle cases, where the charge is small in volume and the powder lays lower than the flash hole when the gun is horizontal. This seems to suggest that the same phenomenae is not possible in a shotshell where the powder is compressed and all unfilled volume is eliminated by the wad being pushed down and the shot/crimp restraining the wad.
If there are other causes of detonation of properly made smokeless powders, I'm not familiar with them.
Nevertheless, it's not apparent to me that the gun had any deficiency in the Pgun blowup.
