Russ: a couple of very helpful graphs.
This from 1931 shows the pressure-distance curves with vintage powders; FFg, Ballistite (Dense) and Schultze & DuPont (Bulk) and DuPont Oval "progressive burning smokeless powder"
The pressure is falling at the forcing cone, though less so with DuPont Oval
Modern powders peak and fall much more rapidly so the pressure at the forcing cone is even lower
So there would be no safety justification for
more wall thickness in the cone compared to the end of the chamber (where pressure is higher)
And to clarify Bruce's point, Bell's study compared 2 1/2” chamber with a 7/16” forcing cone vs. 2 3/4” chamber with a 1” forcing cone and showed the pressure decrease was about 400-1200 psi depending on the load and vv. the pressure rise
could be as much as 1200 psi
A summary is here about 1/4 way down
https://docs.google.com/document/d/1...vwLYc-kGA/edit
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