An armour piercing shell is a type of ammunition esigned to penetrate armour. In naval warfare and older anti-tank shells, the shell had to withstand the shock of punching through armour plating. Shells designed for this purpose had a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge. Some smaller calibre AP shells have an inert filling, or incendiary charge in place of the HE bursting charge. The AP shell is now very rarely seen except in naval usage, and is not commonly used there.