If the Coriolis effect is a significant factor it stands to reason that the end of a rifle barrel moves as the projectile passes through it. Then the target moves. Shooting south the barrel moves the bullet to the left as the target moves to the left.
Wouldn’t this negate the Coriolis effect as a factor in shooting?
Not that Coriolis is a big effect over the range of a gun, but to answer your example, if you were somewhere in the northern hemisphere, the points south of your are moving east at a slightly faster speed than you are, and points north of you are moving east slightly slower that you are. Does that make sense? Obviously the north pole is hardly moving at all (just spinning in place) while the equator is moving at the highest velocity (largest distance form spin axis).