Remember the first Parker Sherman Bell blew up in the destruction tests he reported in DGJ? Blew in the chamber area, basically peeling out from the hole for the extractor rod. I saw a Fox with a similar pressure failure, but it peeled from the outside--because on a Fox, the guide rods for the extractors ride in small channels on either side rather than between the barrels. Obvious weak spot in both cases--"weak" being a very relative term, since it took 30K+ psi to blow Bell's Parker.