My 700 would shoot BH very well. Really do not think you need a mag primer though. The 700 BP is so short regular shot gun primers shoot very well. With a Mag primer you will tend to close the flash channel in the breech plug down very quickly.
No matter which primer you might use you will need to hand drill out/clean the flash channel of the breech plug.
Also I would mention do not try to clean the flash hole with anything metal. It erodes quick enough without helping it get larger. Normal soaking the BP in a cleaning solution after drilling out the flash channel will clear the flash hole. Blowing compressed air through the flash hole will clear it in most cases after soaking