Thanks Roy and Rocketman. I agree that some bulges can be repaired properly. I guess my thought is that since the area bulged in an uncontrolled way, it would be more suspect to me than stronger.I wonder if it's possible for parts of a bulge to be closer to its stress/strain limit than the area in general. Also, the rate that the force is applied would be much quicker when a shell is fired and I'd wonder if that might matter.
Rocketman, just for conversation, I don't believe bridging as you illustrated it would work. Maybe a shot column wouldn't be as porous as a single layer of spheres. Besides, even though the pressure is much less, wouldn't shot always bridge at the choke, for example what steel shot might do.
When I've seen pictures of riveling, it kind of looks like the barrel saw some sort of natural frequency when the particular load was fired. I wonder if the elastic response of the barrel was just set off in an unlucky way to have regularly repeating obstructions with decreasing pressure as the shot moved down the bore. How's that for drivel.
