I use this method alot at our clubs yearly sight-in. Since we allow the gun owners to sight their own guns in, we start them off at 25 yards to make sure their on the paper before they move to the longer ranges. We have them in the black within 2 or 3 shots most of the time. Most are overjoyed to move off the 25yd range so quickly. Every once-in-awhile we have a shooter who fells he/she just has to shoot 5 or 10 round groups to prove to themselves that they're on the mark, they just can't believe sighting their rifle can be done with only a quarter box of shells.
Just a note, we see some shift (generally not a lot, less than a inch or so) in the impact point on variable scope when changing from low to higher powers, so we have our shooters use a mid range power setting to minimize the shift.