Rapid Fire

Rapid Fire is a  Secondary skill in Diablo III.

In-game
While channeled, fires a rapid stream of arrows that deal Physical damage per tick to the first enemy the stream reaches. The arrows do count as missiles, and are properly affected by respective augmentations and restrictions, but each missile actually consists of several arrows, to create a similarly torrent-like graphic.

Runes:

 * Withering Fire: damage type changes to Fire, initial Hatred cost reduces to 10.
 * Frost Shots: damage type changes to Cold, enemies hit by the stream are chilled by 80% for 2 seconds.
 * Fire Support: fires additional two Rockets per tick, each hitting for 145% damage as Physical.
 * High Velocity: damage type changes to Lightning. Each arrow has a 50% chance to pierce through enemies.
 * Bombardment: damage type changes to Fire, and arrows are replaced with grenades, decreasing damage to 545% per tick, but adding an 8 yard blast radius.

Non-rune enhancements:

 * Taeguk (Legendary Gem): increases damage done by 2% per tick (+0.04% per rank) and armor by 2% per tick (rank 25 bonus), stacking up to 10 times. Does not work with Sin Seekers (see below) since no resource is expended.
 * Buriza-Do Kyanon (Legendary Crossbow): each shot will have 1-2 guaranteed pierces (in addition to High Velocity rune effect).
 * Wojahnni Assaulter (Legendary Crossbow): Rapid Fire deals 75–100% more damage for every 0.15 seconds it is channeled, stacking up to 30 times, first stack gained immediately.
 * Mantle of Channeling (Legendary Pauldrons): while channeling Rapid Fire, increases damage done by 20-25% and reduces damage taken by 25%.
 * Sin Seekers (Legendary Quiver): increases damage by 250-300%, and removes the channeling cost.
 * Hellcat Waistguard (Legendary Belt): Bombardment grenades have a chance to bounce 3-5 times, dealing additional 50% damage on each bounce, increased to 800% on the final bounce.

Passives

 * Ballistics: Damage dealt by rockets from Fire Support is doubled.