Can you clarify this? Not sure if I've misunderstood or if we have different interpretations. Aspects, such as one set up by a weapon modification declaration, may be used on any roll which makes sense to the group. Attacks, maneuvers, blocks, etc.
Rolling to attack is not rolling to create an aspect.
There is a reason why attack stunts get a +1 and aspect or defense stunts can be a +2.
For an aspect to be "used", after it is created, one free tag is allowed. After that it requires fate points.
The stunt that the OP is using is pretty much a "permanant" scope that does not have to be rolled on or a fate point to be declared.
His equipment could be a rifle w/ scope. If he has a scope on the rifle, he gets the benefit of being able to aim easier - which translates into rolling for aspects easier.
Is scope User a stunt? I'm not familiar with it.
From what you say, it adds +2 to any gun related maneuvers when using a scope. So I'd say it goes toward your aiming roll.
When you use "in my sights" you roll your guns vs their defense skill(I'm not sure what skill you use to defend). If they fail to defend, you have them maneuvered for a number of exchanges equal to the amount of shifts by which they failed.
Your Stunt would give you a +2 to this roll.
So it's more likely to succeed and be sticky and therefore let you tag your "in my sights" more times.
If this is how the stunt works then this is how you'd do it:
So your character Brian is Guns +5.
He spends a round targeting an enemy 5 (guns) +2(Scope user) =+7 for the maneuver.
In the next round he shoots the enemy 5 (guns) +2 (taggin "in my sights") = +7 vs their athletics dodge.
I you successfully hit, you take the difference of their athletics result and your guns result and the damage is 3 (weapon damage) + (the difference by which they failed their dodge)
NOTE: weapon damage does not increase your chance to hit. It indicates how much extra damage the weapon will do WHEN you hit. So if the difference between your guns result and their Athletics result is 0, then you will do 3 stress to your target.
Your stunt would also give you a +2 to any maneuver using the guns skill. You could:
disarm someone by shooting the weapon out of their hand(i'm not sure this is possible in real life, but they do it in the movies all the time!)
Trip them up by "making them dance" while shooting at their feet etc, etc...as long as your using your scope...
This is correct.
First some info on scopes. Contrary to colloquial usage, scopes don't 'help you aim'. In some ways they make elements of aiming more difficult (there are reasons snipers typically work with a spotter). Scopes simply make it easier to see a distant target. Aiming is about judging distance, knowing how gravity, air, and wind will affect the bullet over that distance, and muscle memory and control used in pointing the weapon and pulling the trigger.
This isn't really relevant to the OP's question, but I have to make a nitpicky correction on the above.
Scopes DO help the shooter aim.
There are more kinds of scopes than just the standard crosshairs. There are red dot scopes and fiberoptic scopes like Acogs.
Snipers work with a spotter because they need protection, someone to use the spotting scope, and because the FOV (field of view) out of a high powered scope is relatively small.
Depending on what a person is shooting at, depending on what the mission is, a scope will almost always be preferable to iron sights. Sure, a high powered scope is not very handy in up-close MOUT style room clearings, but that is what they make these for:
The only reason red dot scopes and such are not used on pistols more often is because it's really hard to find a holster for them. They also make the weapon heavier.