What is the first step in mechanically zeroing the M16/A2?

The first step in mechanically zeroing the M16/A2 involves adjusting the front sight post until it is flush with the housing. This step is essential because the front sight post is the primary aiming point for the rifle, and it must be properly positioned to ensure that shots land where the shooter intends.

By making sure the front sight post is flush, the shooter sets a stable reference point for subsequent adjustments. This flush alignment helps to eliminate any potential height discrepancies that could cause rounds to impact higher or lower than expected when aiming at a target.

After ensuring the front sight post is flush, further adjustments can be made as necessary, such as adjusting the rear sight assembly and the windage knob, but establishing a correctly positioned front sight is critical to achieving an accurate zero.