The command doesn't work with soldier weapons, only vehicle weapons (in Arma 3 at least). The return value is either 1 or 0, very rarely the value falls in between. 1 doesn't mean you are going to hit the target, while 0 means you're definitely off.
Description
Returns how good a vehicle's weapon is aimed at the target.
Syntax
vehicle aimedAtTarget [target, weapon]
Parameters:
vehicle: Object - vehicle only, not unittarget: Objectweapon: String - (Optional) if not provided, checks all weapons; if provided, checks that weapon only
Returns: Number in range 0..1 - 0 if no weapons or if weapon was provided and not found
Examples
Example 1
_aimingQuality = heli aimedAtTarget [target];
Example 2
_aimingQuality = heli aimedAtTarget [target, "M197"];