Interesting discussion. Re the Dupont chart, although the loads in question do indeed swap positions in terms of highest pressure vs lowest, they're actually becoming closer rather than farther apart at the end of the chart. Of course that stops short of any weak point 20" or more down the barrel, but the difference is so small--looks to be only 2-300 psi between the BP load and the highest pressure smokeless load--that it seems to me, unless the curves start moving apart again, it would not be a matter for concern.
Bell did similar tests in one of his "Finding Out For Myself" series in Double Gun Journal. Once again, very little difference in the pressure curve between modern smokeless loads and black--although he also stopped short of showing what happens beyond the 12" mark. However, at that point on his charts, it does not appear that the difference between the loads was increasing; no indication that the modern loads were going to be more problematic farther down the barrel than the BP loads.
