Editing Armour-piercing ammunition (section)

=== APDS ===
{{Main|armour-piercing discarding sabot}}
[[File:24 mm slpprj m49.png|thumb|Swedish armour-piercing discarding sabot projectile, here seen with and without its [[Sabot (firearms)|sabot]] as well as its internal [[tungsten]] core]]
An important armour-piercing development was the ''armour-piercing discarding [[Sabot (firearms)|sabot]]'' (''APDS''). An early version was developed by engineers working for the French [[Edgar Brandt|Edgar Brandt company]], and was fielded in two calibres (75&nbsp;mm/57&nbsp;mm for the [[Canon de 75 modèle 1897|75 mm Mle1897/33 anti-tank gun]], 37&nbsp;mm/25&nbsp;mm for several 37&nbsp;mm gun types) just before the French-German armistice of 1940.<ref>{{cite web|url=http://www.museumoftechnology.org.uk/military.php?cab=shells|title=Shells and Grenades|publisher=The Museum of Technology|location=Old Town, Hemel Hempstead|access-date=2010-10-23| archive-url= https://web.archive.org/web/20101016002149/http://www.museumoftechnology.org.uk/military.php?cab=shells| archive-date= 16 October 2010 | url-status= live}}</ref> 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 and 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 [[Ordnance QF 6-pounder|QF 6-pdr]] [[anti-tank gun]] and later in September 1944 for the [[Ordnance QF 17-pounder|QF-17 pdr]] anti-tank gun.<ref>{{cite web|url=http://www.avalanchepress.com/17-Pounder.php|title=The 17-Pounder|author=Jason Rahman|publisher=Avalanche Press|date=February 2008|access-date=2010-10-23| archive-url= https://web.archive.org/web/20101109112825/http://www.avalanchepress.com/17-Pounder.php| archive-date= 9 November 2010 | url-status= live}}</ref> The idea was to use a stronger and denser penetrator material with smaller size and hence less drag, to allow increased impact velocity and armour penetration.

The armour-piercing concept calls for more penetration capability than the target's armour thickness. The penetrator is a pointed mass of high-density material that is designed to retain its shape and carry the maximum possible amount of energy as deeply as possible into the target. Generally, the penetration capability of an armour-piercing round increases with the projectile's kinetic energy, and 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 armour 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 armour-piercing rounds. Tungsten and tungsten alloys are suitable for use in even higher-velocity armour-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. Aircraft and tank rounds sometimes use a core of [[depleted uranium]]. Depleted-uranium penetrators have the advantage of being [[Pyrophoricity|pyrophoric]] and self-sharpening on impact, resulting in intense heat and energy focused on a minimal area of the target's armour. Some rounds also use [[Explosive material|explosive]] or [[Incendiary device|incendiary]] tips to aid in the penetration of thicker armour. [[High-explosive incendiary/armor-piercing ammunition|High explosive incendiary/armour piercing ammunition]] combines a [[tungsten carbide]] penetrator with an incendiary and explosive tip.

Energy is concentrated by using a reduced-diameter tungsten shot, surrounded by a lightweight outer carrier, the ''sabot'' (a French word for [[Sabot (shoe)|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 calibre, the use of APDS ammunition can effectively double the anti-tank performance of a gun.