D&D4 Wiki
Attack bonus if proficient +2
Weapon die ([W]) 1d6
Type ranged
Range 10/20
Handedness one-handed
Proficiency category simple
Weapon group
Weapon property load free
Price 1 gp
Weight 0 lb.

A sling is a simple one-handed ranged weapon in the sling weapon group.[PH:218]

Loading a sling is a free action requiring the use of both hands.

Ardents, artificers, assassins, avengers, bards, battleminds, bladesingers, clerics, druids, fighters, invokers, paladins, psions, rangers, runepriests, seekers, sorcerers, swordmages, vampires, wardens, warlocks, and warlords are proficient with all simple ranged weapons, including the sling.

Rogues receive proficiency with the sling directly.

Other classes do not have proficiency with the sling as a class trait, but any character can become proficient by taking a Weapon Proficiency feat.