Sling: A sling is little more than a Leather cup attached to a pair of strings. Your Strength modifier applies to Damage rolls when you use a sling, just as it does for thrown Weapons. You can fire, but not load, a sling with one hand. Loading a sling is a move Action that requires two hands and provokes Attacks of Opportunity.

You can hurl ordinary stones with a sling, but stones are not as dense or as round as bullets. Thus, such an attack deals Damage as if the weapon were designed for a Creature one size category smaller than you and you take a –1 Penalty on attack rolls.