I don't think MCBANE is speaking of bore sighting a new scope, just the desired zero to best acheive best long range hits.
MC, the answer is, there is no answer to the question as you state it. The path of a round nose 30-30 bullet won't be anywhere close to a pointed bullet in a 7m magnum. Each bullet, its velocity AND the scope or sight height above line of bore affects where you will get best zero results for any cartridge.
You need to find a ballistic chart for your cartridge and bullet, that will usually give you good approximations of where to zero for long range work. Many reloading manuals have ballistics tables and books like Shooter's Bible/Gun Digest give us the charts for factory loads. See if you can't find what you need there.