Firstly, estimating the distance to the target is critical at longer ranges, because the difference in the point of impact between 400 and 500 yards is 25–32&thinsp;in (depending on zero), in other words if the shooter estimates that the target is 400&thinsp;yd away when it is in fact 500&thinsp;yd away the shot will impact 25–32&thinsp;in (635–813&thinsp;mm) below where it was aimed, possibly missing the target completely.