TennesseeNuc,
You are indeed correct that the conversion number has to do with the bullet obturating, that is, the base being "smashed" to fill the rifling fully and allow for a good seal as the bullets travels the barrel. An example of its use is: Pretend you cast a bullet of BHN 10. You multiply that times the conversion factor and you get 14220 P.S.I. to obturate the bullet. If you are shooting a reload that produces 12000 P.S.I. the bullet may not obturate. If you are shoot a reload that produces 15000 P.S.I. the bullet, in theory, will obturate.
I think this is just a guide and not an absolute. Good-luck...BCB