Armor-piercing Shot and Shell - History

History

The late 1850s saw the development of the ironclad warship, which carried wrought iron armor of considerable thickness. This armor was practically immune to both the round cast-iron cannonballs then in use and to the recently developed explosive shell. The first solution to this problem was effected by Major Sir W. Palliser, who invented a method of hardening the head of the pointed cast-iron shot. By casting the projectile point downwards and forming the head in an iron mold, the hot metal was suddenly chilled and became intensely hard (resistant to deformation), while the remainder of the mold, being formed of sand, allowed the metal to cool slowly and the body of the shot to be made tough (resistant to shattering).

These chilled iron shots proved very effective against wrought iron armor, but were not serviceable against compound and steel armor, which was first introduced in the 1880s. A new departure therefore had to be made, and forged steel rounds with points hardened by water took the place of the Palliser shot. At first, these forged-steel rounds were made of ordinary carbon steel, but as armor improved in quality, the projectiles followed suit.

During the 1890s and subsequently, cemented steel armor became commonplace, initially only on the thicker armor of warships. To combat this, the projectile was formed of steel—forged or cast—containing both nickel and chromium. Another change was the introduction of a soft metal cap over the point of the shell.