So let's say I have Reckless aim and Startoss shower using both of these let's assume I'm attacking enemies only in melee does it effects stack for reducing my ac? What about the plus is it only a +2 or nothing on iterative targets?
Reckless Aim (combat)
Your lack of regard for others proves a boon when you fire projectiles into melee.Prerequisites: Point-Blank Shot, Precise Shot.
Benefit: When you shoot or throw ranged weapons at an opponent engaged in melee, you can choose to take a –1 penalty to your AC and gain a +2 competence bonus on your attack roll. However, when you roll a natural 1 on a ranged attack roll made with this bonus, you automatically hit a random adjacent creature that threatens your intended target.
Startoss Shower (Combat)
You can strike multiple opponents with thrown weapons.Prerequisite(s): Dex 13, Point-Blank Shot, Startoss Comet, Startoss Style, Weapon Focus with the chosen weapon, base attack bonus +4.
Benefit(s): When you hit an opponent while using the Startoss Comet feat, you can continue to make attacks against foes that are within one range increment of all previous opponents. You determine cover for each attack from the most recently hit foe’s space instead of your space, and you cannot attack an individual foe more than once during this attack action.
You can make a maximum number of attacks equal to 1 + 1 per 5 points of base attack bonus you possess. If you have Vital Strike, Improved Vital Strike, or Greater Vital Strike, you can add the additional damage from those feats to the initial ranged attack (but not any subsequent attacks).
Reckless aim isn't vital strike or a feat in that line, the bonus should apply for all attacks against enemies engaged in melee. You only take the AC penalty once, whether you're doing a normal full attack or a startoss comet/shower attack, but the natural 1 hitting a random creature threatening your target applies to all attacks against enemies engaged in melee.
God that feat is awfully written/edited.
The only sensible way to rule it is to have the feat behave like Deadly Aim, i.e. act as if the sentence "You must choose to use this feat before making an attack roll and its effects last until your next turn." were part of the description.
Concur.