Bill,
Low pressure ammunition is just that, UNTIL there is an obstruction in the bore.
When that happens, it isn't.
The only blown up guns I've seen were right here in cyberspace, save a long ago article in the DGJ on a Greener Empire that was blown up, with an accurate description of how it happened, and the sleeving of that gun. I've seen plenty of guns of all types with bulged barrels. For what it is worth, alot of the pictures of blow ups make only generic reference to what cartridge was being used at the time.
A very good English gunsmith working in the states told me he would be a much, much poorer man were it not for Americans with a reloader and an English double gun. Of course, the regulars here, there, and everywhere will then take great offense, and go on to tell you how they have been reloading for (insert multiple digit number, here) years, and they have never, ever had a mishap.
Then, just as regularly, we see a catastrophy, like this.
I can tell you every kind and type of cartridge loaded into any of my guns for the last decade, at least. Note the generic reference to ammunition used, in this event. I still would need more information than that to make any kind of accurate conclusion, or blame any one individual,
But, we don't even have a notion of what ammunition was being used in the gun. And, I doubt we are going to get it.
Makes you wonder.
Best,
Ted