Moses, the problem would be that if you could get a pressure figure from period literature (where's Drew when we need him?), the pressure would be as measured by lead crushers rather than the current piezoelectric method. You come up with a figure that's like the old LUP (lead units pressure) that you used to see in old reloading manuals. You can't get an exact conversion, but you can guesstimate close enough to get you into the ballpark. And then back off some to build in a safety cushion.