Mark: Remember that if you're using 2 3/4" hulls in a 2 1/2" chamber, you need to build in an additional margin of safety. Sherman Bell's tests with longer hulls in shorter chambers showed that you can get an increase of 1,000 psi vs the same load fired in a 2 3/4" chamber. I'd agree that generally speaking, 8,000 psi "book value" is probably a good place to draw the line. That'd mean 9,000 psi factoring in an extra 1,000 psi for the longer hull.