The base style? Not at all.
Sniping wrote:
If you've already successfully used Stealth at least 10 feet from your target, you can make one ranged attack and then immediately use Stealth again. You take a –20 penalty on your Stealth check to maintain your obscured location.
ACTION
Usually none. Normally, you make a Stealth check as part of movement, so it doesn't take a separate action. However, using Stealth immediately after a ranged attack (see Sniping, above) is a move action.
Overwatch Style wrote:
You have learned to wait until your ranged attacks have the greatest effect.
Prerequisite(s): Precise Shot, Rapid Shot, Weapon Focus with the chosen weapon.
Benefit(s): While using this style, as a full-round action you can ready two ranged attacks with the chosen weapon, each with its own triggering event.
You take a –2 penalty on attack rolls made with these readied actions.
Special: A character with this feat and the weapon training (bows, crossbows, or firearms) class feature can use Overwatch Style with any bow, crossbow, or firearm, respectively, in addition to the chosen weapon.
Overwatch Vortex is the same thing, but 4 attacks. Overwatch Tactician is at least not immediately disqualified.
Overwatch Tactician wrote:
You quickly prepare to react to your enemies' actions.
Prerequisite(s): Overwatch Style, Precise Shot, Rapid Shot, Weapon Focus with the chosen weapon.
Benefit(s): While using Overwatch Style, you can ready two ranged attacks as a standard action, rather than a full-round action.
But it still doesn't work, because sniping is very specific on "one attack", not "one standard action". And the action you're taking with Overwatch Tactician is Ready, not Attack.
