[J.B. Books]

I am not engineer and have no experience or training in the physics and engineering involved with a barrel burst. What I find counterintuitive as a layman is the amount of pressure required to burst a fluid steel barrel is around 30,000 psi per Sherman Bell's destructive tests. How is it that a shot charge and wad being pushed by a force between 11,000 and less than 30,000 psi wouldn't dislodge and send a thin plastic base wad stuck in the bore out the muzzle before it reached a level of barrel burst pressure? Serious question looking for an answer. Perhaps the answer is the pressure builds faster than the ejecta moves but I don't know that.