Mil dots can be very accurate if you know the size of your target. Break the space down between the mils are far as you can. When I taught at sniper school we had the students break them down as far as 1/20 of a mil.
Keep in mind that even if you know the size of your target; your reading can be skewed because of being slightly above or below the target.
The electronic gadgets are great, but they have taken the art out of long range shooting.
USMC Scout Sniper 88-94
Instructor 1st. Mar. Div. SS school 91-94