larry;
I seriously doubt that these pressures stated in this Army Ordnance publication were LUP pressures. These pressures are stated to be from the 1925 British Rules of Proof. Consider the the mean working pressure of Factory Loaded shells in 12ga for 2 5/8", 2 3/4" & 3" are given respectively as 4Ľ, 4 3/4 & 5 tons.
These are not pressures we normally associate with LUP pressures of that era but are much more in line with actual PSI. These as stated are the Service pressure for the ammunition which is slightly lower than the mean working pressure of the gun itself. The mean Proof Pressure of these three lengths of 12ga shells are 6.1 (13,700), 7.1 (15,900) & 7.75 (17,300) tons.
"IF" these are LUP pressures the Brits weren't loading to lighter pressures than us, We were loading lighter than they.
Although admittedly not in common usage at the time, transducers were around by 1925 I believe & apparently this Army Ordnance publication made use of them.
