Hold on a second. Seating OUT decreases pressure, as long as you aren't jammed into the lands... correct? Greater area inside the case with the bullet seated longer=less pressure? Seating deep, less area inside the case=greater pressure?
and P= Higher MVs...correct?
NO, not correct, and as always it's not that simple. And like most such topics its been done here over and over by folks who know more than I do but I read their stuff.
Best general discussion is Brownell's Pressure Factors in its multiple incarnations. Much of the other writings are take offs from Brownell's writings either in conjunction with Wolfe or previous professional articles.
Increased space behind the bullet tends to reduce pressure just as at the same time
reduced space ahead of the bullet tends to increase pressure. And of course increased space ahead of the bullet tends to reduce pressure at the same time reduced space behind the bullet increases pressure - ceterus paribus.
For a great many people much of the time the increased space ahead of the bullet - think freebore or Weatherby style throating - dominates and so pressure (which is pretty hard to define CUP, LUP, Psi, Psia, peak or area under the curve) is reduced. But don't bet your rifle your eyes and your life on it.