I had read of this phenomenon years ago, I believe in a "Rifleman" magazine article which was trying to explain why some fairly light weight obstruction like a little snow could cause a rifle to explode.
Apparently, I'm not alone in this belief.
In a Topic on the Civil War Reenactors Forum where they were discussing a India made Bess exploding a guy called tompritchett said,
"I have hesitated to comment on this thread because it is readily apparent that we do not have the whole story. However, I would like to comment how a blockage could easily cause such a rupture, especially if the blockage was somewhere up the barrel from the powder. When the pressure wave from the exploding black powder hits a blockage somewhere up the barrel from the point of ignition, it bounces back with much or all of its intensity back to the breech plug, then back towards the blockage again, then back towards the blockage and so on until the blockage is totally cleared (the degree that the full intensity of the wave is reflected back is determined by degree that the blockage is either moved by the initial pressure wave or by how much of the wave can escape around the blockage).. Through a process known as constructive interference these pressure waves can reinforce each other as they pass creating at different locations in essence a series of "rogue" waves which can momentarily have a pressure several times greater than the original pressure created by the ignition of the gun powder. It is this rogue wave that then causes the barrel to burst."
This was followed by comments by a Curt-Heinrich Schmidt who wrote,
"In my experience, I haver seen, or heard of a barrel bursting without "blockage." Force generally takes the path of least resistance- that being exiting out the muzzle. However, "force" in the form of pressure and pressure waves can build up and exert pressure in other directions other than the muzzle. (And a caplock's cone flash channel or flintlock's touch-hole is not sufficient to vent or relieve rapidly building pressures...)
Sometimes, the pressure builds at right angles to the obstruction, and creates a visible "ring" behind where the obstruction was. There is a cannon tube in the Gettysburg NPS visitors' center that suffered such a burst."
Now, maybe we are wrong about this however I do know that sonic pressure waves exist and they can be quite useful.
Take the "tuned exhaust" often used on racing engines for instance. On 2 cycle machines these are often referred to as Expansion chambers.
When the exhaust valve/port opens the high pressure gas starting to emerge into the pipe creates a high pressure wave that travels the length of the exhaust pipe at sonic speeds.
When it reaches the end of the pipe a negative (vacuum) pressure wave or almost matching the strength of the high pressure wave is created. This negative pressure wave travels back up the exhaust pipe at a sonic speed and if it reaches the still open exhaust valve and passes into the combustion chamber while the intake valve is opening it will draw fresh fuel/air into the chamber. It in effect becomes a supercharger and the added power is often referred to as "coming on the pipe".
OK. OK. Enough about engines and back to ramming the ball without powder.