One other point, there is a point (unknown to me) of diminishing returns when it comes to case capacity.
Consider the Colt Walker, 60 grains of (black) powder, .45 caliber. Modern "equivalent" is the 45 BPM - black powder magnum - http://en.wikipedia.org/wiki/.45_Bla...agnum_(.45_BPM
Compared to the .45 Colt: http://en.wikipedia.org/wiki/.45_Colt
50% more powder, how much higer velocity with the 250gr bullet?