That is a really nice shotgun sling timpa.
Actually not just a shotgun sling. Queue sling is right - that should give you a fan shaped dispersion area.
A disc sling, hmmm.
Okay, challenge accepted.
Got a couple different ideas.
You either make a matched pouch and ammo (pretty simple, like a mini clay pigeon launcher) or try and make a pouch that will hold a variety of different sized discs.
A bit trickier, so I'll go for that one.
To give you a clue how my mind works, I'm pretty sure it'll be nicknamed: the hedgehog pouch.
Makes sense right ?