Actually I've done that with bond1s Staff (from the store) turned into a flak weapon ---> this thread:
http://forum.thegamecreators.com/?m=forum_view&t=187770&b=24
The download link still works.
I used a small sphere made with Entity Workshop as the projectile.One problem I could not overcome though, is that every projectile gets its colour "blackened" and seems to be immune to shaders. I made my own /flak folder btw and it worked flawlessly - at least with 1.18
In case you find my grammar and spelling weird ---> native German speaker ^^