Sling as a weapon is relatively not well known although was used effectively by the middle east peoples and Egyptians since the most ancient times. At the beginning projectiles were raw stones, later carved and around the V C. BC some were made of lead. Excellency as a slinger could only be achieved by means of an intensive training since the more early childhood.
Onasandrius wrote the 1st C. BC in his book "Strategy". "Sling is the deadly weapon used by light infantry because lead is of the same color than air and therefore not visible, impact is unexpected and not only hard but the bullet penetrates deeply into the flesh".

Balearic derives from the Punic "Bale Yarch" literally means "Masters in throwing". Most probably they learned this technique from the Phoenicians or Greeks.
They fought in the 1st and 2nd. Punic war in favor of Carthage but after the Roman conquest served under Roman's legions. On the legions battle order they were in charged to start the hostilities from the flanks even before than the longbow men could do it. When enemy contact was imminent both longbow men and slingers retreated between lines to allow the infantry and Calvary to fight.

While a longbow had an effectiveness up to 100 mts. the Balearic slingers launched projectiles to more than 200 meters far.

Since they were a few years old started the training that will last forever. The first notice of an armored ship was due to Balearic slingers. On the 123 BC. Quintus Caecillius Metellus begun the conquest of the island of Majorca. Believed or not the slingers were able to sink the Roman ships from the coast shooting to the ship hull waterline with lead bullets like this one and other of higher calibers. Quintus had to protect his ships with shields. Only after two years Majorca was finally conquered.

They wore three slings. A large one tighten to his waist (to be used in distances of more than 60 mts.), a small one tighten around his forehead (20-25 mts.) and a medium size one always on the hand (up to 60 mts.). They carried the bullets in a goat fur bag hanging from his shoulder. With the large one they could launch 500 grs. stones (like a tennis ball) able to destroy shields and wood defenses. With the small and medium size slings the lead bullets could perforate at short distances (up to 60 mts.) thin armors and helmets. The sling as a weapon was widely used not only by Balearic warriors but by other Iberian warriors and also by Roman auxiliary troops like Greeks, Sicilians, North Africans but after the Roman conquest of the Balearic Islands elite slingers were always Balearic as those fighting in the Julius Caesar legions. Bullets in Spain are usually found on the known battle fields of the Roman conquest. Roman bullets are commonly engraved Iberian never.

Two fine examples of almond shape small caliber war sling lead bullets to be used with the small sling. Have a good ballistic coefficient (C) according to their caliber. With concretions. Ca 150 to 45 BC

From left to right:

Measures: Thick: 16x9 mm. Length: 29 mm. Weight: 18.3 C=117
Thick 14 x10 mm Length: 29 mm Weight: 21.5 C=149

Ballistic coefficient C = P/D**2 Being P weight in Kg. and D diameter in mts. An standard rounded lead bullet of the Napoleonic wars had a C of 104.