Hi!
I use to boresight them on the air. Speed around 260-280 Knots (to give u time to change the rack), altitude 6000-8000, and range 4-5 nm. I get the best results with this method, and i also use home airbase after airborne for boresighting. Doing it on the ground seems to get worst parallax effect, same with range above 6 nm or less than 3. To be honest i tend to boresight as close as i can get as using AGM65 to strike something.
Cheers
Milker's post in agm65 irl was marked as the answer