1925 - 1954 12g barrel flats marked with chamber length and 1 1/8 or 1 1/4 oz.
In 1925, 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.
Definitive Proof remained 6 1/2 Drams BP with 1 2/3 oz. shot
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)
Definitive Proof - 7 1/2 Drams BP with 2 oz. shot.
John Brindle, author of
Shotgun Shooting: Techniques & Technology published a review of Proof and Service pressures in Part 5 of his series in
The Double Gun Journal, “Black Powder & Smokeless, Damascus & Steel”; Volume 5, Issue 3, 1994, “Some Modern Fallacies Part 5”, p. 11.
His estimated
post-1954 but pre-CIP standard shotshell pressures by LUP converted to piezo transducer PSI
……………Standard Service…..Max. Service…....Proof
12g 2 1/2”…….6,800 psi…………8,800 psi…….12,250 psi
12g 2 3/4”…….7,800 psi…………9,800 psi……..14,050 psi
(
CIP 2 3/4”)….10,733 psi….…..12,328 psi……13,489 psi
16g 2 1/2”…….7,300 psi…………9,300 psi……..13,150 psi
16g 2 3/4”…….7,800 psi…………9,800 psi……..14,050 psi
ed: your "search for knowledge" is simply an effort to draw attention to yourself, and you are most welcome to do your own research and reach your own conclusions. Let us know when you come up with a "summary" that suits you.
It's all here just for the looking, and I'm done
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