Interesting looking at loads I, J & K, all 2 3/4" service loads with 1 oz of shot, that the J load of 28 grains Ballistite showed a lower pressure than either the Oval or DuPont Bulk smokeless. The Ballistite load would have been approximately a 3 dram equivalent load & & it gave a pressure of 10K . Not positive if this should be considered actual psi, but likely from that era was LUP.
Ballistite was a relatively fast powder but not likely much more so than the DuPont Bulk. Oval was a "Progressive" powder (Slow) & it showed the highest pressure (13K), though the actual load was not listed, perhaps a higher velocity load than the other two.
All the proof loads were with Hercules 3FG Black with pressures ranging from 14K up to 17K.
In a test run by DuPont a few years earlier, using 1 oz of shot but with velocities all held to the same level (3 DE) Ballistite did show a higher pressure than Oval. In that one tests were done with Oval, Ballistite, Infallible, DuPont Bulk & 3FG Black.
The load with Oval had the lowest pressure of all in that test & it was stated that was an Under Load for that powder. All other pressures as I recall exceeded 9K in that test. These did have a slightly lower powder charge than the Hunter Arms test as 3 DE versus 3 DE for the Hunter tests, with the Oval likely being at least a 3 3/4 DE or perhaps even 4 DE which would account for its higher pressure.
Amazing consistency between the two actually. Note that in the Hunter tests all loads hit their peak pressure in less than 2", which is also quite similar to the DuPont tests. The Gunmakers knew what they were doing when they Beefed up the chamber area of a shotgun barrel with the adoption of Smokeless powders.
Note also on the 4 service loads H, I, J & K that while they start at 3K apart, by 4 inches the gap had dropped to about 2K, @ 5 inches to about 1K & closer from there to the muzzle.
As I have said so many times here on this forum those who insist on using those very low (Peak) pressure loads because they are concerned with a low minimum wall thickness half way down the barrel are simply NOT doing the gun a favor. While admittedly the gap at that point is small, but, if the same ballistics are kept the pressure down the barrel will actually be higher the lower the peak pressure is. A careful study of these graphs show it all.
