Although the large cache from the North Camp do not include any of such bullets, some more of those "terror weapons" were unearthed at the South Camp this year.
"We can now definitely link the sling bullets from both Roman camps with those found on the native hillfort," Nicholson said.
A lead or stone bullet could reach speeds of up to 100 mph when shot by expert slingers. The largest stones were the size of lemons, while the smallest were acorn-shaped and were slung in small groups of three or four as form of grapeshot.
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Specialized units of auxiliary troops were recruited to fight alongside the Roman legions, with the most feared and expert slingers coming from the Balearic Islands.
According to John Reid, of the Roman heritage group the Trimontium Trust, it is becoming increasingly clear the bullets were deposited in a single brief episode.
"This greatly strengthens the suggestion of a Roman assault on the hill top which appears to have been occupied at that time," Reid told the BBC.
Preliminary analysis indicates that archaeologists may be able to associate this event with the Roman conquest of Southern Scotland by the emperor Antoninus Pius around 140 A.D.
"We now know it wasn't a siege or a battle but an assault. They attacked and massacred the native Celts, probably all done within five days," Nicholson explained to the Daily Record.
"It is really exciting because this means the assault on Burnswark was the start of the Antonine campaign -- the invasion of Southern Scotland and the construction of the Antonine Wall," he added.
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