I think it is in Bob Bristers book on shotgunning where he did the math supporting what Dean says about the lead difference between lower and higher velocity shells. That book is a real classic and a must read for any shotgunner IMHO. Sure straightened a lot out for me, and especially on lead and horizontal shot stringing. I started experimenting on leading ducks wayyyy more on long crossing shots than I had been after reading that and it worked.

Spock out - time to go look for a moose....

Manufacturer's don't list the pressure on there boxes for a couple of reasons. First and most important. Pressure readings can vary between pressure barrels which leads to the second reason Lawyers.