AIM-9B doesn't like maneuvring targets, even not too violent turns may render it a miss. I tried it on Su-25, MiG-15 and L-39, MiG sometimes get hit, Su-25 is easier to hit but it can trash the missile too, especially with flares, I never have been able to hit L-39 with it.
Apparently in new update just released today, 3D model and performance of AIM-9B is adjusted, wonder how will it act now
BTW, D changes gunsight mode, to switch to missiles, you change another knob, not that one, "SAFE, CAMERA, GUN, MISSILE" was the name of correct switch IIRC. Don't know if new patch fixes it but, there wasn't a control assignment for this in options, so it was only a mouse clickable knob.