1 click = 1/4" at 100 yards on the 4200. Sighting in 3" would be a point and shoot to 300-350 Yards - zero would probabbly be 250-275 I would say for the 270WSM. If you see shots of the 300 yard range and are comfortable with taking those shots, 3" high is good. If your not comfortable or won't see these longer range shots as a rule I would go 1.5" high. Some feel over compensating is better, however I am not one of them I set my zero to match my area(s) and abilities. Also consider when free handed it a lot of shooters tend to pull up when firing, actually causing you to shoot even higher...this is why I am not a big fan of over inching your zero. For me I would much rather know what my bullet will do at my comfortable ranges and just concentrate on putting the hairs where they need to be vs how high or low on the animal. I set my zero accordingly. Hit the range you have loads of time to find your spot prior to this fall.