let's say you have expose, fire control, and gunner on the Falcon. Can you choose to roll less dice than you weapons value? Could you expose as your action which would give you 5 attack dice at range one, but choose to only roll one dice. That would be your first attack and you would get a target lock from fire control. If that one dice came up anything but a hit or a crit, that would trigger gunner. On the second attack you could roll the full 5 dice and have the target lock to re-roll non-hits.

On the other side of the coin, let say you have a three agility and you are being attacked by this Falcon. If it rolled only one hit on it's first attack, can you choose to roll no defense dice and take one hit. Not risking what might come from a second attack from a 5 dice roll with target lock?

No.

Ref: Rules reference page 5:

Roll Attack Dice: The attacker rolls a number of attack dice equal to its primary weapon value; if it is attacking with a secondary weapon, it rolls attack dice equal to the attack value on that weapon’s Upgrade card instead.

No. You must roll the correct amount of dice. You could choose not to use Expose as your action (and you should, it's terrible), but that's it.

If you have rerolls you can reroll hits.

How are you using FCS on Han, he doesn't have the System slot...

How are you using FCS on Han, he doesn't have the System slot...

Pff... Only if you follow "the rules"

like they said you have to throw all the dice, but there are other options to help you blank those dice, accuracy corrector if you have a systems slot, as you don't have to add the hits after canceling your dice, of course that means you won't have a FCS, the other option and best way to do this is zuckuss crew, in combination with bossk and gunner or IG88 you can force your opponent to reroll his evades, then gain focus TL from bossk for your second shot

let's say you have expose, fire control, and gunner on the Falcon. Can you choose to roll less dice than you weapons value? Could you expose as your action which would give you 5 attack dice at range one, but choose to only roll one dice. That would be your first attack and you would get a target lock from fire control. If that one dice came up anything but a hit or a crit, that would trigger gunner . On the second attack you could roll the full 5 dice and have the target lock to re-roll non-hits.

On the other side of the coin, let say you have a three agility and you are being attacked by this Falcon. If it rolled only one hit on it's first attack, can you choose to roll no defense dice and take one hit. Not risking what might come from a second attack from a 5 dice roll with target lock?

I hope it has been established that if you are supposed to roll X number of dice you MUST roll all of them. There may be ways to negate or reroll them later but you still have to roll them all.

Now when I read the part I added BOLD to I wonder if you are playing Gunner incorrectly. Trigger Gunner happens if the Attack misses. You could roll [hit] [hit] [hit] [hit] [crit] for some attack and still have the Attack miss despite of of those good dice results. When you ask about rolling fewer defense dice it seems that you understand this but that sentence makes it seem like just rolling a [boom] or [kaboom] is going to prevent Gunner from triggering. This is a misconception that some new players have which is why I'm addressing it.

Just to be clear it is possible for an attack to "hit" even if it rolls all Blanks. The example I'm thinking of may not have Gunner available but it is just to show that what the dice roll isn't all that determines if an attack hits.

To be even more clear on the subject of Gunner and hitting, 'hitting' in X-wing is very specifically defined as there being uncanceled hits or crits after all attack and defense dice modification has been done. The symbols we shorthandedly call 'hit' and 'crit' aren't actually called that anywhere in the rules, they're just symbols that instruct you on what type of damage card to pull.

A roll of [hit] [hit] [crit] that is countered by a roll of [evade] [evade] [evade] will have Missed and triggers Gunner because there was no uncanceled damage, while the same attack roll opposed by [evade] [evade] [blank] counts as a Hit because there was an uncanceled result.

if you have a way to on the fly mod your number of dice, sure you can purposely throw less dice to invoke gunner.

If you dont have a way to mod your number of dice, no, you must roll your attack value.