Armour-piercing discarding sabot
To further enhance their armor-penetration capabilities, APDS rounds typically feature a hardened core made from tungsten or another hard, dense material.
[2] APDS rounds remain in use for small or medium calibers, such as in saboted light armour penetrator (SLAP) ammunition.
[3] Armour piercing discarding sabot munitions were developed to increase penetrating performance of anti-tank projectiles by generating higher impact 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; however Brandt himself used term "propulsive basal member" in his English patents), that was retained for the duration of the flight until impact.
[5] [a] The sabot of a large calibre APDS consists of a light high strength alloy full diameter pot and base unit, which is screwed together.
The rear half has a rubber obturator and driving band (again nylon) held in place by the screw-in base unit.
When a large calibre APDS is fired and while still within the bore, the setback forces shear the forward petals, partly unlocking the sub-projectile from the sabot, but still holding it rigidly within the pot.
Once outside the barrel, the pins, centring band and forward petals are released or discarded by projectile spin, the aerodynamic drag removes the pot/base unit.
As an APDS sub-projectile does not require driving bands and the core is supported at the base and ogive region, a far more aerodynamic projectile shape can be chosen.
The sequence upon impact of the APDS projectile, for example the 120 mm L11, as used on the Chieftain tank, fired L15 APDS [6] (muzzle velocity 1370 m/s), goes as follows: the lightweight ballistic cap is crushed, the penetrating cap then strikes the armour, distributing the shock across the whole surface of the core's nose, reducing the initial shock experienced by the core.
37/24 indicates full-calibre with sabot and sub-caliber without sabot — 37 / 24 mm (1.46 / 0.945 in).
Left object shows the projectile with sabot, central object shows projectile without sabot and the right object is the projectile's tungsten -core.
