Here's an article on Wm. M. Caldwell and Speer's device. BBHFarm Gallery :: Pressures and the Revolver, Gun Digest 1973 Edition

I just re-read that article and the findings there. One thing that jumped out was the reference on the first page to solid test barrels that had been used, presumably in Speer#8 and in Speer's ammunition development. The other thing is the correlation to what Lee Jurras was doing with Super Vel, i.e. using smaller diameter bullets, with lighter weights and longer OAL to reduce pressure.