Load your mag full with 4, then push down on the stack of cartridges so they're below the bolt and push the bolt forward a bit. Then you can drop a round into the chamber and finish closing the bolt...the extractor will snap over the rim when you close the bolt just as it does when chambering a round pushed up from the mag.
(Note, this is only for a push-feed design like the 700, preMkII Ruger M77s, or 110 Savage. Don't try to push-feed with a Mauser-type claw extractor...it's very hard on them and you can booger the rim or extractor up pretty good if you jam things too hard.)
Easiest way...stick with four in the mag and an empty chamber. If four didn't get the job done, one more probably isn't the magic ticket.