Kutter;
The lead crusher did not give actual PSI, even though in its day it was often stated as such. The more correct label is LUP's (Lead Units of Pressure). 3 long tons tons is 6720 lbs. The formula which Drew cited is one which was done by the British when they began using the Piezo Electric (PE) method & was derived by taking pressure by "Both" methods simultaneously. It was never stated to be an exact formula but "Close Enough" for pressures within the normal range of a shot gun. It is as far as I know applicable only to pressures listed in British tons. As noted running the formula for three tons came within 22 lbs of that cited by the proof house, while the mere expedient of adding 1,000 lbs still misses the mark by more than 1,200 lbs, not even in the same Ball Park. When lead crushers were being used they were calibrated by what was essentially a static pressure, but in taking the pressures from the barrel the pressure was on them for so short a time they simply did not reach full compression, thus LUP's always read less than actual PSI. The PE gauges read virtually instantaneous & give true PSI readings.
