Some years ago, one of the Italian makers, I believe then A&S, had some barrel failures with their modern guns. They went to a Vaccum Melted Process on their steel for barrels as they wanted the barrels to last several lifetimes.
So that does tell us that even in modern times, that defects do happen with barrels. Then you attribute the barrel failures to very thin walls, the problem can be multiplied.
I would bet that lots of reloaders use faster burning powders that generate near maximum, when they could go to a little slower powder and drop pressures considerably. But lots I have talked to, say it takes too much powder get the same velocity, thus too much cost. They are usually high volume shooters.
