Thanks John!
The above chart is measured in inches from the breach. I'd love to have one of those test barrels!
For all 4 powders the peak pressure is reached no more than 1 and 1/2 inches from the breach. That distance is not far from the top of the powder charge as measured from the base of the shell. Hmmm, maybe that's why the chambers of barrels have much thicker walls than do the rest of the barrels...
