>> Never saw a cylinder failure like that, though
The particular design of the barrel probably dictates exactly how the barrel will fail (in the event of a failure).
It appears that there was a design flaw that left a weakness at that particular point in the barrel ... so, when it exploded, it did so through the weakest spot. Not sure if it is a flaw in the design of the gun, or the manufacturing of that particular piece. But, that doesn’t look like a standard jammed-barrel explosion.
SnakeDoc
I have never heard of a plugged barrel causing this type of CYLINDER failure.
I have seen several of these types of CYLINDER failures and they all were the result of overcharged/overpressure cartridges, all the result of new handloaders not following appropriate loading procedures.