Here's the long previous thread about 2" shells
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=630238

I looked through my wall thickness data and couldn't find a measurement of a 2" end of chamber
Lots of fluid steel 2 1/2" from .090 to .105 or so.

In 1935, the Proof House determined the 2” “cartridge loaded with full 2 1/2” charge may shortly be a standard British cartridge (and) proof of the 2” gun should be identical with the 2 1/2”’.
The proof pressure for the 2 1/2” cartridge was lowered in 1954 to 3 tons = about 9000 psi service and for the 2” cartridge to 2 3/4 tons = about 8,300 psi service.

In 1955 Burrard reported actual shell pressure measurements for the 12g 2” 7/8 oz. 2.36 Dr. Eq. at standard service 6,440 psi and max. service 8,960 psi.

CIP pressure standards for 2", 2 1/2" and 2 3/4" are the same; Maximum Average (SERVICE) Pressure 740 BAR = 10,733 psi; Maximum Statistical Individual Pressure 850 BAR = 12,328 psi

SO it is very likely that 2" end of chamber and 9" MWT are no different than 2 1/2"

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