Piper and I rarely agree ,but in this case I think he is correct in his hypothesis. Had I had a similar barrel bulge I would have suggested that it was ,a, a hang fire,delayed detonation, the primer had pushed the charge and shot load out of the case before full ignition.Or,b, The gun had been shot with the barrels heavily oiled . As the gun was being used I would summise the former. However when shooting you rarely notice the different sound of a cartridge detonation ,or should I say you do not nesseseraly differentiate. One last piont ,that unless you did notice a specific difference in sound and unles you inspect after each shot ,you will not know when the damage actualy coccured.
