Muskegman,
Yes, the "pressure inside the case is equal in all directions." But that is true of the eventual maximum pressure. Initially, pressure always finds the path of least resistance.
In this instance that's through the flash-hole, rather than at the other end of the case where the bullet starts moving. Even in very small calibers, the bullet is not only heavier than the primer, but usually held far tighter by the case neck, because of more contact with the neck and, sometimes, crimping. (It takes a lot more force to seat a bullet than a primer.)
Plus, the normal "high" primer of fired .30-30 cases indicates the primer was backed out the initially relatively low pressure.
Well, I'm going to respectfully disagree again. There are two forces at play to get either the primer or bullet to start moving - (1) you have to overcome the static friction holding it in place, and (2) you have to overcome the inertial mass. The primer starting to move first is because the force holding it in place (friction) is lower AND the inertial mass is lower. It's not because the pressure is higher down near the primer.
Where's Denton when you need him?
