Are we talking about peak pressure here? Recalling Bell's "Finding Out for Myself" tests, he used several strain gauges positioned at various points along his test barrel, which is how he got readings from the chamber as well as much farther down the barrel. If you can do that with one strain gauge, wonder why he used several? (Maybe improved technology?)
I submit the above while admitting that I know zilch about strain gauges. But the Bell tests (and I believe also some done by Dupont, going way back before WWII I think) showed peak pressures much closer to the breech--like within the first couple inches--for all powders.
From other information I've seen, those pressures sound low for factory loads.
