Sounds to me like you are doing things correctly - my impression is that they are not terribly reliable being so old. Just to confirm, I'm assuming you are always firing from behind the target? (They are rear aspect only, won't event track an oncoming or flanking target.)
I have pretty good luck firing from ~1.6-3 KM, and hit probably 80% of the time, but this is against AI F4's that don't go particularly evasive. Against aggressively maneuvering targets I just stick to pew pew.