You can find it in **WoD: Armory** on page 53:

> A character must have Firearms 2 with a Revolvers Specialty to fan. She may expend three shots to fire a short autofire burst. If the revolver has at least six shots loaded, she may completely empty it to fire a medium autofire burst (see p. 160, the World of Darkness Rulebook). In either case, fanning raises the revolver’s Strength requirement by 1. A dramatic failure while fanning may result in the character snapping off the hammer or slapping the gun out of her own hand to land at an enemy’s feet.

One of the first supplements for **The World of Darkness 2nd Edition** will be **Hurt Locker**, which is billed as a 2e replacement for the *Armory* and *Armory Reloaded* books. I imagine any updated rules will be found there when it comes out.