Armour-piercing discarding sabot (APDS) is a type of spin-stabilized kinetic energy projectile for anti-armour warfare. Each projectile consists of a sub-calibre round fitted with a sabot. The combination of a lighter sub-calibre projectile with a full-calibre propellant charge allows for an increase in muzzle velocity compared to full-calibre rounds, giving the round increased armour-penetration performance. To further enhance their armour-penetration capabilities, APDS rounds typically feature a hardened core made from tungsten or another hard, dense material. For a given calibre, APDS ammunition can effectively double the armour penetration of a gun when compared to full-calibre rounds such as AP, Armour-piercing Capped (APC), and Armour piercing Capped Ballistic Cap (APCBC) projectiles. APDS-rounds were commonly used in large calibre tank guns up until the early 1980s, but have since been superseded by armour-piercing fin-stabilized discarding sabot (APFSDS) projectiles, which use fin-stabilization and can be fired from smoothbore guns. APDS rounds remain in use for small or medium calibres, such as in saboted light armour penetrator (SLAP) ammunition. History and development Armour piercing discarding sabot munitions were developed to increase penetrating performance of anti-tank projectiles by generating higher impact velocity. A larger projectile would require a completely new weapon system, but increasing velocity faced the limitation that steel armour-piercing (AP) projectiles shattered at velocities above about 850 m/s when uncapped. Tungsten carbide, with twice the density of steel, was seen as a solution, due to its greater hardness and ability to withstand shock and pressure, but its greater weight reduced velocity. In the 1930s, to increase terminal velocity without increasing diameter, engineers working for the French Edgar Brandt company developed "saboted" ammunition, in which a heavier sub-calibre core was surrounded by a lightweight "sabot" (the French word for a clog or the hard outer layer of hooves), that was retained for the duration of the flight until impact. They fielded two calibres; the 75 mm/57 mm for the 75mm Mle 1897/33 anti-tank gun and 37 mm/25 mm for several 37 mm gun types just before the French-German armistice of 1940, before evacuating to the United Kingdom, to join ongoing anti-tank ammunition development efforts there. The British term for this construction was "Armour-Piercing, Composite Rigid" (APCR) While the sabot improved short range effectiveness, the additional drag caused the performance of the shot to fall off dramatically with increasing range. Between 1941–1944, Permutter and Coppock, two designers with the UK Armaments Research Department (ARD), developed