We are told that the "normal" Celts (as usual, they tend to do things akwardly on this island...
) know and can use the sling as a weapon by JC (not the Israeli, the Roman one). Vercingetorix, leader of the Gauls against the Roman Invasion called for reinforcement, including archers and slingers. So we have slingers, who can use their slings against "two-legged big game" in case of emergency.
We also have stones and clay bullets around
oppida or other fortified places...
But we don't have any sling nor any how-to-sling-like-a-true-Celt, not even a drawing on a pottery shard.
JAG wrote on Sep 25
th, 2014 at 5:40pm:
Some people trace the words on a page. Others retrace the footsteps of their ancestors.
And some try their best at the later with whatever traces on pages their ancestors' neighbourgs left. And a lot of tests.