PeteM;
I believe if you look closely at the 2 charts you will see that powders B, C, D & E of the original with 5 powders listed became A, B, C & D in the newer chart. When the 2nd chart was published the powder A (Ballistite or equiv) had been discontinued & was dropped. The testing was done by DuPont de Nemours & Co, with the 2nd chart showing only 4 of the powders from the test being published by The American Rifleman in the 1950's.
You will note that powder A on the chart did exceed 10K pressure, but this was a 3 DE load pushing 1Ľoz of shot, not a pip-squeak load by any means. I believe that Hercules Red Dot powder is very closely related to the old Ballistite. I have some 50+ year old data giving loads for Red Dot with 1Ľoz of shot. With todays components it is pushing it to keep pressures in line with 1 1/8oz loads & it seems to be most useful for 1oz or under loads.
It doesn't take a very thick wall to contain 3K pressure, but I would not want it to be very thin at that point either, better safe than sorry.
Once you get out beyond about 15" then bbl wall thickness is more for rigidity, dent prevention & general integrity of the bbls, than for containing pressure.
