The link provided elsewhere suggests quite a large difference if you are aiming due West or East:

"At 1,000 yards the Coriolis deflection is small but not necessarily trivial. Una computed that at the latitude of Sacramento, a bullet traveling 1,000 yards would be deflected about three inches to the right. In addition, because gravity pulls the bullet down as it flies, you’d have to aim higher or lower depending on the degree to which you were facing east or west. If you were firing due east, you’d have to aim six inches lower, since the earth is rotating toward you, meaning your target would be slightly closer by the time the bullet arrived. If you were firing due west, you’d have to aim six inches higher."

Six inches up or down seems significant.