Armour-piercing fin-stabilized discarding sabot

As an armament for main battle tanks, it succeeds armour-piercing discarding sabot (APDS) ammunition, which is still used in small or medium caliber weapon systems.

Improvements in powerful automotive propulsion and suspension systems following World War II allowed modern main battle tanks to incorporate progressively thicker and heavier armor, while maintaining considerable maneuverability and speed on the battlefield.

The logical progression was to make the shot longer and thinner to increase its sectional density, thus concentrating the kinetic energy in a smaller area.

As more structurally efficient penetrator-sabot designs are developed their length tends to increase, in order to defeat even greater line-of-sight armour depth.

Depleted uranium alloy, for example, is pyrophoric; the heated fragments of the penetrator ignite after impact in contact with air, setting fire to fuel and / or ammunition in the target vehicle, contributing significantly to behind-armour lethality.

Although both materials have nearly the same density, hardness, toughness, and strength, due to these differences in their deformation, depleted uranium tends to out-penetrate an equivalent length of tungsten alloy against steel targets.

[6] The use of depleted uranium, in spite of some superior performance characteristics, provokes political and humanitarian controversy, but remains the preferred material for some countries due to lower cost and greater availability than tungsten.

In some countries, such as South Korea, specific heat treatment processes such as multi-stage cyclic heat treatment[7][8] and microstructure control are applied to tungsten penetrators to finely separate metallic grain structures, significantly improving the mushrooming deformation, which was a chronic problem for conventional tungsten alloys, increasing penetration by 8–16% and impact toughness by 300%.

[citation needed] Often the greater engineering challenge is designing an efficient sabot to successfully launch extremely long penetrators, now approaching 80 cm (31 in) in length.

[13] The discarding sabot petals travel at such a high muzzle velocity that, on separation, they may continue for many hundreds of feet at speeds that can be lethal to troops and damaging to light vehicles.