Hallo Thearos!
even in Italy - thus I don't remember when, exactly - have been found a few lead bullets with holes in the edges. Some archaeologists think that they are bullets, some other that they are weights, some other that they are ex-voto.
Howewer, I'm sending you a PM with the bibliography, that is too long to post it here  
I hope you'll enjoy, and keep searching for other studies about this argument!
Greetings,
Mauro.

Thanks, Mauro, for the general bibliography on Gravisca. But what is the reference for a bullet mould in C5th context, among the long list of titles ?

A quick Google search for "Gravisca piombo ghiande missile" reveals in fourth place an article by L. Fiorini and  M. Torelli in a journal called Facta, 2007. I reproduce his picture of the "bullet tree". The reference is Gravisca 16 (Bari, 2004), p. 65.  
 
 
All thanks to Mauro to pointing this out. But I need to look up the publication-- does this date to the early C5th, like so much else in the "foundry' area of the Gravisca shrine which Mauro mentions ?
 
 

I looked up Gravisca 16. There is one single find of a sling bullet, and the "colata di fusione", the lead pour "tree" from a sling bullet mould.  
 
From the publication, I can see where it's been found (sector AB), perhaps the year (1977, if that's what the inventory means). But there's no stratigraphical datation; on the contrary, the publication refers to late Classical and Hellenistic parallels (Olynthos, Peiraieus...).  
 
The shrine area has finds from C7th to late Hellenistic. I suppose these sling bullets could date from any date within this period; at least, it's not clear from the publication when to date them.  
 
Why does this matter ? Just to establish that these are not necessarily the earliest securely dated lead sling bullets, and not necessarily from a C5th or early C5th context.

Thanks for that, v. helpful