Can a TL from fire control system be spent right away for a reroll?
FCS...get a TL after an attack ,then use it same round to refill?
No....ish
FCS gives you the target-lock after the attack, so it cannot be used on the attack that generated it.
If you would be able to spend a target lock later that round (due to, say, an R7 astromech or a second attack from a Gunner), you CAN spend the TL on that one.
Can a TL from fire control system be spent right away for a reroll?
The answer to the question you asked is "Yes, but...." The answer to the question I think you were trying to ask is "No."
As soon as you have the Target Lock from FCS there's nothing to prevent you from spending it, just as soon as you have an opportunity to do so. Said opportunity can't come from the attack that triggered FCS, though, because FCS triggers after the attack. If you have some ability that lets you get another attack (TLT, Cluster Missiles, Gunner + I missed, Corran Horn, etc...) then you could use the new Target Lock on the second attack. See "Buzzsaw" in the slang thread.
Edited by digitalbuskerPerfect. Thank-you fellas