The bullets were used approximately 1,800 years ago and were discovered at Burnswark Hill in southwestern Scotland. What actually happened at Burnswark Hill is up for debate. Some scholars claim that the Romans launched a massive attack at native Scots, others claim it was Roman training post. Regardless, there were a lot of Roman soldiers there.
One element of the Roman attack was the slingshot, although their militarized iteration is much different that say, Bart Simpons. The Romans used something called a fustibalus, a stick sling. The largest stones it hurled were the size of lemons and the smallest, presumably used for a scattering effect in close quarters, were the size of acorns. Expert slingers were recruited from the Balearic Islands in the Western Mediterranean, where parents would force their children to earn food by knocking it over with a sling first.
Researching the stones at Burnswark Hill, archaeologists couldn't help but notice one thing: the holes. Twenty percent of all the lead sling stones they found had holes drilled into them. "It's a tremendous amount of work to do, to just chuck them away," says archaeologist John Reid of the Trimontium Trust, a Scottish historical society directing the Burnswark Hill site.
An early theory suggested the holes were used for holding poison. But "the holes are too small, and there's no guarantee that these are going to penetrate skin," Reid says. "And they are ballistically inferior: They don't fly as far, don't fly as fast and don't have the same momentum [as larger sling bullets] — so why put poison holes in only the little ones?"
Eventually Reid's brother, an avid fisherman, weighed in. He thought the holes be used for noise. "I said, 'Don't be stupid; you've no idea what you're talking about. You're not an archaeologist,'" Reid jokes. "And he said, 'No, but I'm a fisherman, and when I cast my line with lead weights that have got holes in them like that, they whistle.'"
"Suddenly, a light bulb came on in my head — that's what they're about. They're for making a noise," Reid says.
Reid describes the stones as "terror weapons," designed to create a horrifying sound in battle as they are tossed over the enemy's head. The more noise and confusion on the battlefield, the better for the famously disciplined Romans.
Regardless of the specifics of Burnswark Hill, the Romans and the Scots remained in battle for more than 20 years. "Scotland is rather like Afghanistan in many respects," Reid ssays. "The terrain is pretty inhospitable, certainly the farther north you go, and the isolation and long supply lines would make it difficult for servicing an army that far north." The Romans would have needed any psychological advantage they could get.