Would not the increases in velocity have a direct relationship with a fouled bore creating more pressure even with lighter primers?

In a sealed system the strength of the primer would increase velocity as the primer power was increased would it not. To me that would make sense regardless of vent hole size.

In a flintlock I could see the liner size haveing a direct influence on velocity as gasses are vented through the vent rather than the bore.

I sometimes think of these things while bored at work.