Your fingers are so nimble that reloading your sling is almost effortless for you.
Benefit: You can load a sling or double sling as a free action. This does not provoke attacks of opportunity. This feat allows you to fire your sling as many times in a full-attack action as you could attack if you were using a bow.
Pathfinder Player Companion: Halflings of Golarion. Copyright 2010, Paizo Publishing, LLC; Authors: Hal MacLean and Amber E. Scott.