2 5/8" or 2 3/4 " Chambers?

[Drew Hause]

John: please add another 0 to your psi rise.
Scroll down about 1/3 here for a summary of the Bell study
https://docs.google.com/document/d/1...vwLYc-kGA/edit
The greatest rise was a 7/8 oz. Estate plastic hull at 1206 fps at a 1216 psi increase.
“Shooting 2 3/4” shells in 2 1/2” chambers does make them produce more pressure-but in most cases it is less than a 1000 psi increase. I see no reason, related to safety, to modify an original 2 1/2” chambered gun to shoot 2 3/4” shells, if the 2 3/4” load you intend to use would develop pressure that is safe in that gun, when fired in a standard chamber!”

To the 2 5/8" chamber question. Yes, the 2 5/8" chamber was designed for roll crimped 2 5/8" or 2 3/4" shells. Most modern 2 3/4" plastic hulls are less than 2 3/4" after firing however



I am aware of no study reporting an increased pressure using 2 3/4" plastic hull shells in a 2 5/8" chamber.

I believe 2 5/8" in Ahmerkan is also 2 5/8" in English

British 2 1/2" and 2 5/8" chambers did have different Maximum Service Loads; the 1925 - 1954 Rules of Proof
The 2 1/2” & 2 5/8” 12g maximum service load was reduced to 3 Dr. Eq. with 1 1/8 oz. shot with a mean pressure of 3 1/4 tons by LUP = 9,800 psi by Burrard’s conversion.
The 2 3/4” 12g max. service load was 3 3/8 Dr. Eq. with 1 1/4 oz. shot with a mean pressure of 3 1/2 tons = 10,640 psi by Burrard’s conversion. (Primarily for heavier “Waterfowl” guns)