I can do it regularly with the german rockets, its a matter of practice.. do it this way:
Approach the bomber from behind, keep it steady halfway down (or maybe even 2/3s down) the lower dash (the line going down from the circle) from the aiming reticle (zoom in to get better accuracy). Just when the range jumps from 1.5 to 1.0 fire off rockets with 2 sec. spacing.
Of course this depends a little on altitude and overtake speed. Also its only viable against a non-maneuvering target.
Have fun,
Litjan