High-explosive incendiary/armor-piercing ammunition (HEIAP) is a form of

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

which combines armor-piercing capability and a

high-explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

effect. In this respect it is a modern version of an

armor-piercing shell Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, and vehicle armour. The first, major application of armour-piercing projectiles was to defeat th ...

. The ammunition may also be called semi-armor-piercing high-explosive incendiary (SAPHEI). Typical of a modern HEIAP shell is the

Raufoss Mk 211 The Raufoss Mk 211 is a .50 BMG (12.7×99mm NATO) multi-purpose Anti-materiel rifle, anti-material high-explosive incendiary/armor-piercing ammunition projectile produced by Nammo under the model name ''NM140 MP''. It is commonly referred to as ' ...

designed for weapons such as

heavy machine gun A heavy machine gun (HMG) is significantly larger than light, medium or general-purpose machine guns. HMGs are typically too heavy to be man-portable (carried by one person) and require mounting onto a weapons platform to be operably stable or ...

s and

anti-materiel rifle An anti-materiel rifle (AMR) is a rifle designed for use against military equipment, structures, and other hardware (materiel) targets. Anti-materiel rifles are chambered in significantly larger calibers than conventional rifles and are employed ...

s. The primary purpose of these munitions is armor penetration with better beyond-armor effects. Similarly to SLAP rounds (

saboted light armor penetrator The saboted light armor penetrator (SLAP) family of firearm ammunition is designed to penetrate armor more efficiently than standard armor-piercing ammunition. In the US it was developed by the Marine Corps during the mid/late 1980s and was approv ...

) which get their armor-piercing ability from the propulsion of a 7.62 mm

tungsten Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...

heavy alloy

bullet A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. They are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax; and are made in various shapes and constru ...

from a 12.7 mm barrel (.50 caliber) using a

sabot Sabot may refer to: * Sabot (firearms), disposable supportive device used in gunpowder ammunitions to fit/patch around a sub-caliber projectile * Sabot (shoe), a type of wooden shoe People * Dick Sabot (1944–2005), American economist and bus ...

with much more energy than is usually possible from a 7.62 mm round, HEIAP munitions utilize a similar theory with an added explosive effect at the end. The special effect is developed when the round strikes the target. The initial collision ignites the incendiary material in the tip, triggering the

detonation Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with ...

of the HE charge. The second (

zirconium Zirconium is a chemical element; it has Symbol (chemistry), symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyis ...

powder) incendiary charge will also ignite. This burns at a very high temperature, is not easily extinguished, and can last up to 15 minutes. The remaining element of the round is the

tungsten carbide Tungsten carbide (chemical formula: ) is a carbide containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through sintering for use in in ...

penetrator. This has a large amount of

kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...

and will penetrate the armor as a solid-cored armor-piercing shot would. This takes the incendiary material and about 20 steel fragments (created by the explosives), delivering them in a 25–30 degree cone through the armor, increasing lethality. The triggering of the explosive charge is dependent upon the resistance of the target. If the target offers little resistance then the lack of

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

al heating will prevent the incendiary from igniting and the high explosive from detonating. Exploding ammunition was used by both Allied and German forces during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

References

See also