I did NOT say "the pressure is higher down near the primer" I said the powder starts to burn there, so the hot gas expands through the flash-hole quicker than through the neck at the other end of the case. Plus, the primer is obviously easier to push backwards, the reason fired .30-30 cases often show "high primers."
True, you did not exactly say that. You implied that pressure is felt on the primer cup before the bullet base because the powder starts burning (resulting in expanding gas) closer to the primer.
This implies that primer moves back first because it "feels" pressure buildup first (before the bullet feels it). I don't think that's the way things work . . .
