or "generally speaking," the method you describe is correct and reasonably accurate. The exact method is to have someone measure in inches the distance from your sighting eye to the front bead, multiply the distance by 16, and divide by 36 to get the gun muzzle to target distance in yards. Then each inch on the pattern plate will be corrected by 1/16 inch on the stock. The distance from muzzle to target must be 16 times the distance from eye to muzzle.