And of course the Bible
SLING: From ancient times the sling has been the weapon of shepherds (1Sa 17:40) and warriors (2 Ch 26:14)
It was a leather thong or was a band woven of such materials as animal sinews, rushes or hair.
"The hollow of the sling", a widened center part, held the projectile (1Sa 25:29)
One end of the sling might be tied to the hand or wrist while the other was held in the hand, to be freed when the sling was swung.
The loaded sling was whirled overhead, perhaps several times, and then one end was suddenly released sending the missile fordward with considerable force and speed.
Smooth, round stones were specially desired for slinging, though other projectiles were also used (1Sa 17:40)
Slingers were a regular part of the armies of Judah (2Ch 26:14) and Israel (2Ki 3:25)
SLINGER: In early times slingers of stones formed an important part of a military force. The tribe of Benjamin, had 700 picked men, every one of whom was " a slinger of stones to a hairbreadth and would not miss"
(Jg 20:15,16).
The Targums say that the Cherethites and the Pelethites among David's Warriors were adept slingers.
Slingmen where an important part of King Uzziah's military force. (2Ch 26:13,14)
Sennacherib employed a corps of slingers in the Assyrian army, as monuments attest. The fighting forces of the egyptians, Syrians, Persians, Sicilians, and others also had similar divisions. In the Roman army, slinger were among the "auxilia". As late as the 1st century C.E. , Josephus relates that Jewish slingers pitted their skill against Roman forces. -Jewish Antiquities, XVII, 259 (x, 2); The Jewish War, II, 442, 423 (xvii, 5) ; IV 14,15 (i, 3)
In ancient armies the slingers usually made up only one division of the foot soldiers. Archers, as a complement of the slingers, and a smaller number of spearmen completed the infantry. When called forward to begin an engagement or to stall an eney advance, the slingers passed from the rear of the ranks trough corridors among the soldiers. at other times they fired from behind, over the heads of the spearmen. Slingers were specially effective fighters when attacking walled cities. Their missiles, hurled from the ground, could pick the enemy off the walls or reach targets inside the city. (2Ki 3:25)
When siege engines and assault towers were developed, slingers took advantage of the elevated positions their platforms afforded.
An Advantage of the slinger over the armorclad swordsman or spearman was his effectiveness from a distance. It is claimed that their range of effectiveness was up to 122 m (400 ft) with stones, and even farther with lead pellets.
David's use of the sling: Much time and training was required to become a skilled and experienced slinger. Young shepherd boys attending and protecting flocks against beasts of prey developed the needed skill. The shepherd boy David felt much better equipped with his sling than with the heavy armor of Saul. But he doubtless would have been unable to stand before Goliath without faith in Jehovah and strength from him. The outcome of the fight depended, not on the superiority of weapons or upon skill, but upon Jehovah, who supported David. As David called out to goliath " I am coming to you with the name of Jehovah of armies,... whom you have taunted.... And all this congregation will know that neither with sword nor with spear does Jehovah save, because to jehovah belongs the battle"
It was a stone from David's sling, no doubt guided and given unusual force by Jehovah, that sank into Goliath's forehead, striking him down so that david could "definitely put him to death" by Goliath's own sword. (1Sa 17:38-51)
(taken from the book "Insight on the scriptures"