I don't doubt anyones stories, but I have seen a number of buldged barrels, buldged two myself,...
16 gauge 311A SxS. Almost exactly half way up the barrels.
Stuck wad from swollen shells.
12 gauge singleshot Baikal. Water froze in the barrel from ocean spray and snow, 3 inch Black Arrow (cheap shells from a few years back) Swell was 3 inches from the end.
I had gunsmiths work on both barrels. Nothing could be done with the Baikal so I had it cut. The 16 gauge was heated and pounded, it made little difference, but the gunsmith said it did. I have used the gun a hundreds times since without issue. The buldge is very obvious and easily seen from 5 feet away.
I've seen one muzzle loader split from half way back the barrel. I know little about ML's but the guy who shot it said there was a double charge from hunting earlier (?) Whatever it was he had trouble hearing for about 2 weeks and took a real shake from it. He had to go to the doctor to see if he had some kind of percussion injury, again I don't know much about ML's.
I have never seen a buldged rifle, only shotguns. I have witnessed 2 split rifles, and I don't know why it happened, but I know each time they kicked like a horse,
As for shotguns, if you can swell a double barrel within a few inches of the forcing cone, then you really were lucky not be injured. I have seen one gun that this happened with. Belgian 10 gauge sal####er huntung. Pop pulled both barrels and both were obstructed.
These all could very very easily have been avoided by looking down the barrel first. But in the field, I check my barrel now and then or if I fall in the mud or something, but not after each shot
Most obstructions I have heard of and seen and was the case with me and Pop and Dad, were poor storage of Cardboard shells (damp hull of the boat)
I have a swollen 12 gauge shell that now fits in my 10 gauge.