Chuck;
It is amazing how closely the bbl contours of a pre-1900 SxS bbl follow those pressure values. It is also well worth noting that as smokeless powders began to gain wide acceptance gun makers began beefing up the "Chamber Walls" while the rest of the bbl's length remained virtually unchanged. In spite of this so called "Experts" continued trying to scare the public by stating smokeless loads produced their "Maximum" pressures some 10--12 inches down the bbl or right where your left hand was a-holding'er. This chart in fact shows that with all loads giving as near as possible the same velocity to 1¼oz of shot, from the 2½-3" point or about the end of the chamber forward the Black Powder was actually giving the higher pressure, while the smokeless was giving higher pressure in the chamber.
