I have saved a copy of the chart from Bell's article. The important points are that the peak pressures of both (BP and smokeless) powders occurs at about 1" from the breech and they both taper almost in a straight line, to the 12" mark. The loads are 3 drams of fffg BP and 1-1/8 oz. shot and same, using SR7625. I'll try to post the picture, later. Both smokeless and BP pressures follow essentially the same lines. Maybe that's why the barrel wall contours follow nearly identical lines, after 150 years??? The higher pressure of smokeless powder "out by where your fingers are" is total nonsense, as 2-p and others have said.
