The best ancient slingers were known to come from the Balearic Islands, where parents would not allow their young sons to eat unless they could hit the dish of food from afar with a slingshot. The very name of the islands may derive from the Greek "ballein", meaning "to throw". 
In the opening minutes of the disastrous Battle of Cannae, the consul Lucius Aemilius Paullus was hit in the head and killed by a shot from a Balearic slinger. Recent tests showed that a 50-gram sling-bullet hurled by a trained slinger has similar stopping power to a .44 Magnum!
Some wider reading to round off this short thread about ancient slingers: nationalgeographic.com/news/2017/05/a…
“..would have had the same stopping power as a modern .44 Magnum handgun, which fires bullets at speeds of around 1,475 feet per second (450 metres per second) and imparts 1,160 foot-pound force (1,570 joules) of energy.” dailymail.co.uk/sciencetech/ar…
