Ammo noun – Projectiles to be fired from a gun. Cartridge and ammo are semantically related. in small missile topic. In some cases you can use "Cartridge" instead a noun "Ammo", when it comes to topics like projectiles for weaponry.
Cartridge noun – Ammunition consisting of a cylindrical casing containing an explosive charge and a bullet; fired from a rifle or handgun. Ammo and cartridge are semantically related. You can use "Ammo" instead a noun "Cartridge".