From your description of the appearance of the case it sounds as though there was a problem with the ammunition. I would not shoot anymore of those loads. I say this because during the time that I worked in the gunsmithing department at Browning Arms Co. I worked on several rifles that had cases like you describe stuck in the chamber. In many of those cases it was found that the owner had fired the wrong ammo. This took place after Remington renamed the .280 Rem. the 7mm Express, inattentive shooters fired these shells in their 7mm Rem. Mag rifles. The renamed .280 had plenty of room in the larger 7mm Magnum chamber and came apart. I realize that you were firing the correct ammunition in your rifle but the result indicates far too much pressure, perhaps a double charge, wrong powder or some similar was to blame. The swollen case head and destroyed primer pocket are sending a clear message of DANGER which needs to be thoroughly investigated by a gunsmith experienced in this kind of situation.
