Design Armour-piercing fin-stabilized discarding sabot

modern 120 mm tank gun shells

ke penetrators modern tanks commonly 2–3 cm in diameter, , can approach 80 cm long; more structurally efficient penetrator-sabot designs developed, length tends increase, in order defeat greater line-of-sight armor depth. concept of armor defeat using long rod penetrator practical application of phenomenon of hydro-dynamic penetration, (see hydrodynamics). in literal sense, fluid penetration; based on density of target fluid , density , length of penetrator; penetrator continue displace target depth of penetrator length times square root of penetrator target densities. 1 observes longer, denser penetrators penetrate deeper depths, , forms basis development of long-rod anti-armor projectiles. however, practical penetrator , target materials not fluids. nevertheless, @ sufficiently high impact velocity, crystalline materials begin behave in highly plastic fluid-like manner, many aspects of hydro-dynamic penetration apply (anderson 1998, anderson 2016). important parameters effective long-rod penetrator, therefore, high density respect target, high hardness penetrate hard target surfaces, high toughness (ductility) rod not shatter on impact, , high strength survive gun launch accelerations, variabilities of target impact, such hitting @ oblique angle , surviving counter-measures such explosive-reactive armor.

the development of heavy forms of reactive armour (such soviet, later russian, kontakt-5), designed shear , deflect long rod penetrators, has prompted development of more complex kinetic energy penetrator designs, particularly in newest u.s. anti-tank rounds. nevertheless, although penetrator geometry may adapt reactive armor counter-measures, materials of choice deep-penetrating long rod kinetic energy projectiles remains tungsten heavy alloy (wa) , depleted uranium alloy (du). both materials dense, hard, tough , ductile, , strong; exceptional qualities suitable deep armor penetration. nevertheless, each material exhibits own unique penetration qualities may or may not best choice 1 anti-armor application.

for example, depleted uranium alloy pyrophoric; heated fragments of penetrator ignite after impact on contact air, setting fire fuel and/or ammunition in target vehicle, contributing behind-armor lethality. additionally, du penetrators exhibit significant adiabatic shear band formation. common misconception that, during impact, fractures along these bands cause tip of penetrator continuously shed material, maintaining tip s conical shape, whereas other materials such unjacketed tungsten tend deform less effective rounded profile, effect called mushrooming . actually, formation of adiabatic shear bands means sides of mushroom tend break away earlier, leading smaller head on impact, though still mushroomed . tests have shown hole bored du projectile of narrower diameter similar tungsten projectile; , although both materials have same density, hardness, toughness , strength, due these differences in deformation process, depleted uranium tends out-penetrate equivalent length of tungsten alloy against steel targets. nevertheless, use of depleted uranium, in spite of superior performance characteristics, not without political , humanitarian controversy, remains material of choice countries due cost considerations , strategic availability compared tungsten. complicating matters, when foreign deployment of military forces or export sales markets considered, sabot designed launch du penetrator cannot used launch substitute wa penetrator, of same manufactured geometry. 2 materials behave different under high pressure, high launch acceleration forces, such entirely different sabot material geometries, (thicker or thinner in places, if possible), required maintain in-bore structural integrity.

typical velocities of apfsds rounds vary between manufacturers , muzzle length/types. typical example, american general dynamics kew-a1 has muzzle velocity of 1,740 m/s (5,700 ft/s). compares 914 m/s (3,000 ft/s) typical rifle (small arms) round. apfsds rounds operate in range of 1,400 1,900 m/s. however, above minimum impact velocity necessary overcome target material strength parameters significantly, penetrator length more important impact velocity; exemplified fact base model m829 flies 200 meters/sec faster newer model m829a3, 1 half length, wholly inadequate defeating state-of-the-art armor arrays.

often, however, greater engineering challenge designing efficient sabot launch extremely long penetrators, approaching 800 millimeters in length. sabot, necessary fill bore of cannon when firing long, slender flight projectile, parasitic weight subtracts potential muzzle velocity of entire projectile. maintaining in-bore structural integrity of such long flight projectile under accelerations of tens of thousands of g s not trivial undertaking, , has brought design of sabots employing in 1980s readily available low cost, high strength aerospace-grade aluminums, such 6061 , 6066-t6, high strength , more expensive 7075-t6 aluminum, maraging steel, , experimental ultra-high strength 7090-t6 aluminum, current state-of-the-art , incredibly expensive graphite fiber reinforced plastics, in order further reduce parasitic sabot mass, can half launch mass of entire projectile.

the discarding sabot petals travel @ such high muzzle velocity that, on separation, may continue many hundreds of metres @ speeds can lethal troops , damaging light vehicles. reason, in combat, tank gunners have aware of troop over-fire safety.

the counterpart of apfsds in rifle ammunition saboted flechette. rifle firing flechettes, special purpose individual weapon, under development u.s. army, project abandoned.