shooter tilting the rifle, he must correct the fault by holding his rifle so that the sights will be vertical. If the presence of cant is a fact its cause may be differentiated readily by having other marksmen fire test shots as explained, and if the result of the original shooter be corroborated by these marksmen, it is a mechanical defect; but if cant is not detected by these marksmen, the fault lies with the original shooter. The lateral deflection due to 1 minute of cant equals the lateral deflection due to 1 minute in change of sight for a given range multiplied by the height of the continuation of the bore at the same range, and this product divided by the range in feet. Expressed in formula d= h X x m For. 53a in which d is the lateral deflection at the range, X, in feet, h the height of the continuation of the bore at the same range, X, and m the lateral deflection at the same range due to 1 minute in change of sight. For illustration, the angle of departure for the .30-150-2700-C-.389 for 800 yards is 32.5 minutes. The triangle solved gives 22.8 feet the value of h at 800 yards; m for 800 yards=8x1.047-8.4 inches Hence, d= 22.8 2400 x 8.4.08 inches. 1° 60x.08 4.8 inches. |