I can't tell for sure but it looks like something caused a pressure peak at that point in the barrel (an obstruction)and therefore the burst. Perhaps a better gun would not have given way completely just bulged or if the barrels were nice and heavy perhaps shown little effect? Another common occurance is that the shooter has seldom checked before hand for a obstruction and after the incedent usually can't remember anything helpful either, for several reasons. It is highly unlikely anyone is going to say afterward " yeah I saw something in the barrel but thought I would shoot it out". Another problem with getting a quality reason for the failure through the legal system is that the both the plaintiff and the defense will have their experts and those experts with offer contradictory analysiss. So we get to choose! I do remember Remington was sued over defective barrels on the inexspensive shotguns and paid out millions in a class action suit to anyone owning one of their guns, even though those same Remingtons are being used by those who collected the money and are being used with the original barrels. Pat's friend may just want to know what happen so wants to send the gun for tests? The real cause is not likey going to be determined from the photo, legal action or by pricing the gun.
