Although I'm not loading PP, here's what I did with my BC.
I sized an empty case so that the 405gr. RNFP bullet I was wanting to load, would slide in with slight thumb pressure.
I then just barely started the bullet in the case (no powder).
I then chambered it and let the lands push the bullet into the case as necessary.
Then the cartridge was removed and measured. It measured 2.665.
So now I assume that I can load it to anything equal to, or less than, 2.665, with that same bullet.