Eug;
Extremely interesting. I also noted on the obstruction study that peak pressure occured @ 22mm ahead of the leading edge of the obstruction. I recall the explanation from this in Burrard as the fact the rapidly moving charge upon striking the obstruction of course started it moving but was slowed in the process. Takes that much movement for the gases to "Pile Up" behind the wads creating the high localized pressure point.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra