If you are wanting to get him to 700, you might want to rethink your rifle choice as well.
The Remington is a good rifle, but to be consistent a 700 it helps to start with a custom or semi custom rifle, great optics, Then it's trigger time.
It will also hep to have proper training. I had a student just last week, that had never shot past 300 yards, making first round hits at 800 yards in variable winds with his 308.
Optics, I consider Leupold to be entry level, and Nightforce to be the be all-end all. Seekins rings and bases, aftermarket trigger.
Keep him under 400 yards at this point is my suggestion.