page_title: Armor-piercing shell
section_title: Armor-piercing discarding-sabot
hierarchical_section_title: Armor-piercing shell / Types / Armor-piercing shot / Armor-piercing discarding-sabot
caption_attribution_description: English: Armour-Piercing Discarding-Sabot /Tracer round for 17-pounder gun (WW2), with its tungsten carbide core. Sabot marked: APDS/TQF17PR&amp;77MMCDNMK1&lt;Canadian Arsenals trademark&gt;4
context_page_description: An armor-piercing shell, armour-piercing shell in Commonwealth English, AP for short, is a type of ammunition designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships and cause damage to the lightly-armored interior. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions. AP rounds smaller than 20 mm are typically known as "armor-piercing ammunition", and are intended for lightly-armored targets such as body armor, bulletproof glass and light armored vehicles. The AP shell is now seldom used in naval warfare, as modern warships have little or no armor protection. In the anti-tank role, as tank armor improved during World War II newer designs began to use a smaller but dense penetrating body within a larger shell. These lightweight shells were fired at very high muzzle velocity and retained that speed and the associated penetrating power over longer distances.
  An armor-piercing shell must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened body with a specially hardened and shaped nose.
context_section_description: An important armor-piercing development was the armor-piercing discarding sabot (APDS). An early version was developed by engineers working for the French Edgar Brandt company, and was fielded in two calibers (75 mm/57 mm for the Mle1897/33 75 mm anti-tank cannon, 37 mm/25 mm for several 37 mm gun types) just before the French-German armistice of 1940. The Edgar Brandt engineers, having been evacuated to the United Kingdom, joined ongoing APDS development efforts there, culminating in significant improvements to the concept and its realization.  The APDS projectile type was further developed in the United Kingdom between 1941-1944 by L. Permutter and S. W. Coppock, two designers with the Armaments Research Department. In mid-1944 the APDS projectile was first introduced into service for the UK's QF 6 pdr anti-tank gun and later in September 1944 for the 17 pdr anti-tank gun. The idea was to use a stronger and denser penetrator material with smaller size and hence less drag, to allow increased impact velocity and armor penetration.
  The armor-piercing concept calls for more penetration capability than the target's armor thickness. Generally, the penetration capability of an armor-piercing round increases with the projectile's kinetic energy and also with concentration of that energy in a small area. Thus, an efficient means of achieving increased penetrating power is increased velocity for the projectile. However, projectile impact against armor at higher velocity causes greater levels of shock. Materials have characteristic maximum levels of shock capacity, beyond which they may shatter, or otherwise disintegrate. At relatively high impact velocities, steel is no longer an adequate material for armor-piercing rounds. Tungsten and tungsten alloys are suitable for use in even higher-velocity armor-piercing rounds, due to their very high shock tolerance and shatter resistance, and to their high melting and boiling temperatures. They also have very high density. Energy is concentrated by using a reduced-diameter tungsten shot, surrounded by a lightweight outer carrier, the sabot (a French word for a wooden shoe). This combination allows the firing of a smaller diameter (thus lower mass/aerodynamic resistance/penetration resistance) projectile with a larger area of expanding-propellant "push", thus a greater propelling force and resulting kinetic energy.  Once outside the barrel, the sabot is stripped off by a combination of centrifugal force and aerodynamic force, giving the shot low drag in flight. For a given caliber, the use of APDS ammunition can effectively double the anti-tank performance of a gun.
caption: Armour-Piercing Discarding-Sabot /Tracer round for 17-pounder gun (WWII), with its tungsten carbide core
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