"Those are the actual PSI( pounds per square inch )"
Note that if these are LUP pressures then they "Are Not" actual psi. We poor peons will never sort all this out until the makers & proof houses decide to use correct terminology. 1 actual psi should be 1 psi whether measured by SAAMI, CIP or whoever. Some 40 yrs ago we of the US quit using the psi term except on those pressure recorded by the tranducer method which repotedly gives correct readings. Others are listed as LUP's or CUP's depending upon the crusher metal. The 14.503 conversion factor between psi & bar is based upon "Actual Correct" pressure readings, not crusher pressure.
Precisely! What B&P is doing--quite easy to see, from their charts--is a straight conversion from bars to psi. What we know, from the Birmingham Proof House, is that the bar readings are not always transducer measurements. If they're crusher measurements, then the formula does not yield the answer in REAL psi. That's why our reloading manuals specify pressures in either psi or, occasionally, in LUP. If it's in LUP, then we know that figure was arrived at under the crusher rather than the transducer system, and about the best we can do is a "ballpark" conversion to psi by adding 1,000. Build in something of a fudge factor to be on the safe side and that's good enough for reloading purposes. But as we've seen from the Brits, if we assume crusher bars to be transducer bars and attempt to do the math, we're going come up with a psi total that's quite a ways off--although at least it's off on the safe side.
Still awaiting a reply from the Birmingham Proof House. I'll post it as soon as I hear. I think all of us that play with older Brit guns would like to have some more definitive answers.
Last edited by L. Brown; 04/04/07 04:36 PM.
