okay here's my finding in this area.
in front approach (head to head) with stock sparrows (semi active homing missile), a kill is nearly impossible (can't get one to this moment), as soon as i get a lock the ai beam my radar and break the lock and the sparrow go fool.
with a amraam (active missile homing), even if my radar lose the lock, the missile still track the target and mostly hit it
but i notice a thing, when you make a rear approach, you can achieve successful sparrow kills (did it several times), the ai still try to beam your radar but seems to not be able to do it as well as in front approach (but they could do it). Aand you can achieve kill even against target equipped with chaffs (but always in the rear sector)
i notice too in the weapon editor that the sparrows are limited as "rear sector 60°" only, i think they should be all aspect (but i doubt it will change anything in the front sector area)
Now what i get to try is to get and try to kill a target flying in a perpendicular way to me.