Thank you greener4me
Much our verbiage is in trying to clearly document the loadings and service pressures of the 2" guns. I'm mostly trying to help borderbill not blow up his 2 incher
The Proof House declared in 35' that 2" would be proved at the max. service pressure of 2 1/2" (and 2 5/8") guns = 3 Dr. Eq. with 1 1/8 oz. shot = 3 1/4 tons by LUP or about 9,800 psi by Burrard's conversion.
What we STILL don't have is documentation of the proof pressures for the 2" loads prior to 1954, and Bro. Venters was looking. The service loads were 7/8 oz., 1 oz. and 1 1/8 oz. It appears that the proof pressures were the same, but we also don't know the powder load for the 3 loadings.
Henry Sharp in
Shooting Times, 1939 listed 2 loads for the 2":
26 grains Curtis’s & Harvey “Diamond Smokeless” with 7/8 oz. shot = 2.36 Dr. Eq
28 grains "Empire" with 1 oz. shot = 2.55 Dr. Eq.
1947 edition of Burrard's
The Modern Shotgun lists a "Low Velocity: 2" load with 2.2 Dr. Eq. (24 grains of a 33 grain powder) and 1 oz. shot. No pressure was provided.
The "highest mean service pressure" for the 2 1/2” cartridge was lowered in 1954 to 3 tons - 8,960 psi and for the 2” cartridge to 2 3/4 tons = about 8,200 psi.
Standard service is about 75% of max. service
The 1955 edition of Burrard's lists standard load & pressures for 2" cartridges at 7/8 oz. 2.36 Dr. Eq. (26 grains of 33 grain = 3 Dr.Eq. powder) Service 2.25 tons = 6,440 psi; Max. Service 3.0 tons = 8,960 psi.