Head to Head situations are best avoided. This an example of how not to do it!

The best practice is to aim to fly about 50ft to one side, then as the distance closes to about 2000ft (don't forget the closing speed is faster on head to head than normal) give enough rudder to 'Yaw' the aircrafts crosshairs onto the target.

Depending on how far to the side of your target you are give the required 'lead' and open fire.