When boresighting the 81mm mortar, what deflection is indexed on the M67 sight?

When boresighting the 81mm mortar using the M67 sight, it is essential to align the sight with the barrel to ensure accurate aiming and firing. The correct deflection that is indexed on the M67 sight during this procedure is 0000 mils. This represents the zero point for deflection and serves as a reference to ensure that any adjustments made during firing are in relation to this neutral alignment.

Setting the deflection to 0000 mils allows the crew to establish a baseline before making any further adjustments based on target location or environmental factors. It eliminates any potential bias or misalignment that could lead to inaccurate mortar fire. Thus, having this initial setting at 0000 mils is crucial to achieving precise aiming and effective engagement of targets downrange.