The FAQ has updated this card which now reads.
If a ship equipped with fire control system and weapons engineer attacks, that ship must acquire the first target lock on the defender (if able) before acquiring a target lock on the second ship.
If a ship equipped with fire control system attacks more then once in a round, it may acquire a terget lock after each attack. It may spend the target lock acquired after the first attack on the second attack.
B-wing + Fire Control System + Heavy Laser Cannon
So my question is..................a B-wing with a Heavy Laser Cannon and Fire Control System shoots at range 3 rolling 4 dice for the HLC. It can't attack more then once in a round. After adjusting crits to standard hits, which effectively ends this attack the FCS now allows you to gain a target lock. This attack is now finished..............can the target lock attained (after the first attack) now be used to reroll dice for that first attack?
Reading the process I say no it cannot be used to reroll because the target lock was gained AFTER the first attack was completed, and the ship only gets ONE attack per round.
If possible I hope an official FFG designer or judge can answer this. Thanks