cartridge (shotgun)
Piece of ammunition made up of multiple projectiles (pellets), an explosive charge and a primer, all packed inside a case.
crimping 
Ridged edges of the case that are used to close the cartridge and keep the pellets inside.
pellets 
Small round shotgun projectiles that are sprayed out under pressure from the wad; they are made of lead, copper or nickel.
primer 
Metal part filled with a chemical detonating substance that ignites the powder charge.
wad 
Piece of felt or plastic that separates the pellets from the charge; when moved by the explosion, it drives the pellets forward at high speed.
plastic case 
Plastic cover containing the explosive charge and the cartridge’s projectiles (pellets).