Ron, i think the RA series of scopes has 2 stadia lines somewhere in it that're designed to bracket an 18" tgt. size (back to brisket of a broadside deer), by adjusting the power ring and then read off the yardage somewhere in the optic (maybe on the power ring also...at least that's the system Leupold uses for their RES--range estimating system).
...but there is a way better way to use that optic for rangefinding, and that system is based on the mil-dot mil-ranging formula. If your buddy really wants to get into it, tell him to go here--
www.ottllc.com/specialtypistols/sp20.pdf and study Item C) Reticle Rangefinding. This system allows for the most accurate and flexible system of rangefinding with any reticle that has 2 points or more in it (plex, ballistic, custom, etc.), in variable as well as fixed power optics.
