Help with making a functioning gun using Mythic Artifacts

Shotgun:
  Id: STICK
  Display: '&fShot Gun(Sawed off)'
  Ammo:
    Enabled: TRUE
    Bullet: Ammo-SG
    ClipSize: 2
    AmmoPerItem: 1
  Lore:
  - "&fRequires SG Barrels &fto fire."
  - ""
  - "&7Ammunition 2 / 2"
  - "&7Durability 50 / 50"
  Skills:
  - skill{s=SG-Fire} @Target ~onUse
  - skill{s=SGReload} @self ~onSwing
Ammo-SG:
  Id: fireball
  Data: 0
  Display: '&fBuck Shot Barrel'

SGReload:
  Skills:
  - reloadammo
SG-Fire:
  Skills:
  -...