An artillery round of the type in this story consists of two basic parts...
1) Projectile - if explosive it is referred to as shell. If non explosive it is referred to as shot.
2) Cartridge Case or Casing - Ferrous or non ferrous metal canister containing propellant and ignition primer.
The terminology used in this story is correct.
As it was non-explosive, should that have been called shot and not shell?