doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Birmingham Proof House: 1954 Rules of Proof

Received a reply from them today. Here are the equivalent service pressure values:

3 tons--8,938 psi
3 1/4 tons--9,682 psi
3 1/2 tons--10,427 psi
4 tons--11,917 psi

They also suggest that the above values SHOULD apply to guns proved under the 1925 rules, which were stamped only with chamber length and shot charge. Thus, a 2 1/2" chambered gun, 1925 rules of proof, would be equivalent to 3 tons; a 2 3/4" chambered gun to 3 1/4 tons.

Bro. Larry-I hate to start this all over again, but is that CIP psi or good ol' American SAAMI psi? Thanks!

The working formula quoted in Burrard, said to be derived from simultaneous recordings of both crusher & tranducer pressures ie crusher pressure in tons times 1.5, minus .5 = tranducer pressure in tons. You can then convert to psi by multiplying by 2240. Look at the comparsion with these figures from the proof house;
3 tons = 8,938psi (formula 8,960; PH + 22psi)
3¼ tons = 9,682psi (formula 9,800; PH + 118psi)
3½ tons = 10,427psi (formula 10,640; PH + 213psi)
4 tons = 11,917psi (formula 12,320; PH + 403psi)

Note the slight "Growth" in discrepancy as pressure goes up showing it is not an absolute formula.
On a lark I divided the .5 subtractor by 3 tons & got .16666666. I rounded this up to .17 & then used the formula;
Tranducer pressure = (Cp x 1.5) - .17Cp
"All" four gave results that were within One (1) lb of the proof house pressures.
This gave the subtrction figure for 3ton as .51, 3¼ton as .5525, 3½ ton as .595 & 4ton as .68

Should this be called the Fulks Fudge Factor or Miller's Correction?

jack

Which would indicate that if one loaded to below 7000psi for 2 1/2" chambers there is a bit of a margin for increased pressure due to expansion into the forcing cone. Did I really say that?

Jim

Which would indicate that if one loaded to below 7000psi for 2 1/2" chambers there is a bit of a margin for increased pressure due to expansion into the forcing cone. Did I really say that?

Jim

Drew, those are true psi as SAAMI would state them.