This came up in a tourney this past weekend at my store. We're all fairly inexperienced with the game and weren't 100% sure what to do. 

1. X-Wing player's turn. 
2. X-Wing performs Focus action. X-Wing has pre-existing Target Lock on TIE Advanced from several turns ago.
3. X-Wing shoots at (Target Locked) TIE Advanced at range 1 using primary weapon. Rolls badly with initial roll to hit; 3 misses and 1 hit (can't remember if the misses were blanks or eyeballs).
4. Burns pre-existing Target Lock. Picks up all dice except the one showing a hit.
5. Re-rolls the three misses.
6. Still rolls badly, but now has a couple of eyeballs showing on these rolls.

Can he now choose to Focus and turn those eyeballs into hits on the re-rolled dice or should we have made note of his initial roll for Focus purposes or something? Seems legit from the way we read the rules, but seems almost too good to be true.

The guy using it didn't exploit; he was a brand-new first-timer. After the fact though, it definitely made me raise an eyebrow since Target Lock's verbiage reads that you can re-roll any attack dice you want (as opposed to MUST re-roll any misses), you could make your initial roll, keep hits, crits, and eyeballs, burn the Target Lock, hopefully get more hits, crits, and eyeballs, then burn your Focus token to turn any of those eyeballs into hits.

Seems like a pretty nasty tactic if it's legit! 

 My bad. Should have used search function. 

Sorry!

 Short answer, which you probably figured out (though how you did it with the broken search function on this forum, I don't know): yes.

 I don't think anyone will blame you for not using the search function here, don't worry about it  

This is a perfectly good strategy and almost ensures that your X-Wings will be able to take down a TIE Fighter every round. Against swarms it's almost necessary to take down a ship (or two) every turn, so being able to easily get Focus and Target Lock at the same time has huge payoffs.

Alamoth said:

It's still worth doing, of course. It will almost certainly do 1-2 damage, and likely also strips the TIE's defensive action, making it an easy setup for any other Rebel ship that happens to be nearby. But you shouldn't count on Target Lock + Focus for a kill unless the TIE is already damaged.

Vorpal Sword said:

How much do these odds improve if you are using Wedge and benefit from his ability to reduce the target's Agility by 1?

Alamoth said:

OMG this is bad ass!!  I missed this part completely on the rules….I should have read better. This is a game changer for me. So for clarification sake for a less experienced player as myself.   So for example I got a target lock on a TIE fighter  and I make my attack roll….so im rolling 3 attack dice and only one dice hits……I can then burn the target lock and take the two failed dice rolls and re- roll the two dice that failed and then with the new results of the two dice i get eyballs now if i have a focus token on my x-wing i can then burn the focus token to turn the two eyeballs into hits?  If this is so, I know exactly what i'm going to run in the tournament.

SWEET!  thanks :)

WHY this is correct is found on page 11 in the rulebook, under "Step 3. Modify Attack Dice". It's further clarified on page 12 under "Modifying Dice Results". Target Lock allows you to reroll a die, which can only be rerolled once. Focus allows you to change the result of the die without rerolling it. So as others have said, yes, it is legal to do both on one attack.