were effective against unhardened iron, British doctrine held that only shot (i.e. non-explosive projectiles) were suitable for penetrating the new hardened armour being developed in the 1880s; hence the gunpowder filling was discontinued. References Bibliography "Treatise on Ammunition" 2nd Edition, 1877. War Office, UK "Treatise on Ammunition" 4th Edition, 1887. War Office, UK Projectiles Artillery shells