I think barrel blowups have more to do with the weight of the shot than the base wad moving forward in the barrel. That is one reason it is so hard to determine what caused the catastrophe. The evidence is all over the field.
Many years ago, I worked at a rock quarry. My job was to drill 3-inch diameter shot holes, 25 feet deep, and load them with dynamite and ammonia nitrate. If you didn’t put anything on top of the powder, the explosion would simply go puff. But, put 12 inches of lime dust on top of the powder, and the full force of the explosion would go sideways and fracture the rock.
I think it works the same way in a gun barrel. If a lightweight wad gets stuck in the barrel, the next shot probably pushes the light wad out without a problem. But, put a double load of shot (I don’t know how you could do it) in the shell, and the pressure is so high that the barrel has to give. My guess is the thinner the barrel, the more likely it is happen. Something has to cause the pressure to skyrocket to have the barrel blow up. Nothing spikes pressure more than pushing more weight down the barrel.
Just an idea from an old quarry man.
Many years ago, I worked at a rock quarry. My job was to drill 3-inch diameter shot holes, 25 feet deep, and load them with dynamite and ammonia nitrate. If you didn’t put anything on top of the powder, the explosion would simply go puff. But, put 12 inches of lime dust on top of the powder, and the full force of the explosion would go sideways and fracture the rock.
I think it works the same way in a gun barrel. If a lightweight wad gets stuck in the barrel, the next shot probably pushes the light wad out without a problem. But, put a double load of shot (I don’t know how you could do it) in the shell, and the pressure is so high that the barrel has to give. My guess is the thinner the barrel, the more likely it is happen. Something has to cause the pressure to skyrocket to have the barrel blow up. Nothing spikes pressure more than pushing more weight down the barrel.
Just an idea from an old quarry man.