Armour Piercing (AP)

Armour Piercing ammunition is a blanket term used to describe a wide variety of munitions developed during the Second World War.

At the beginning of the war, armour piercing ammunition (which had been in use from the First World War) consisted of a simple hardened steel projectile which used kinetic energy along to pierce armour. Ammunition was always of fixed (also referred to as Quick Firing) type; ie one-piece ammunition with a projectile attached to a cartridge case. The round operated in the traditional method; a primer in the base of the round was struck by a weapon's firing pin, igniting the propellant in the base of the cartridge.

In time, variations of AP ammunition were developed.

• Armour Piercing Capped (APC): the head of the projectile was protected by a cap which absorbed the initial impact on striking the target.

• Armour Piercing Capped Ballistic Capped (APCBC): As for APC, but with an additional cap to improve the performance of the projectile's flight. As solid shot rounds were found to shatter on some types of improved armour as the Second World War progressed, APCBC was developed to redress this problem. "The cap absorbed the initial impact while the main projectile entered the armour."¹

As armour on German tanks became increasingly thicker, the need to upgrade anti-tank capability increased. The simple expedient of using larger guns was not easily accomplished, given multiple concerns such as weight of the gun, retooling factories to build new weapons, restrictions on turret ring size and the ability to mount larger guns on tanks, etc. Improved munitions, however, brought respectable improvements in armour penetration performance.

• Armour Piercing Composite Rigid (APCR): was an improvement on standard solid shot in which a projectile of smaller calibre than the gun but made of denser metal (such as tungsten) was used. The tungsten core was surrounded by an alloy of lighter metal that was disposed of when the projectile impacted the target.

• Armour Piercing Discarding Sabot (APDS): APDS increased the capabilities of APCR by using a light sheath ("sabot") of metal around the tungsten core of the projectile, which through a combination of centripetal and aerodynamic force stripped off the round right at the muzzle of the gun, lowering the drag of the projectile in flight and increasing its penetrative capabilities.

Notes

1. Henry, Chris. British Anti-Tank Artillery 1939-45 (Osprey Publishing Ltd., Elms Court, Oxford, UK, 2004) ISBN 1841766380 p.40