So that makes sense. The 38 special has a lot of airspace, where the 40 has almost none. I’ve got to stop comparing apples and oranges. It’s the unique case volume, size, and shape, that sets up these weird secondary pressure wave scenarios.
I wonder if the Herco would be better behaved in the 38 special with a wadcutter pushed down all the way flush with the case mouth. If nothing else it creates a different set of conditions.
That is also why a increased loading density in the .357 has maybe a different effect on pressure.
Hmm, stuff to think about.
Josh