An
armor-piercing shell is a type of
ammunitionAmmunition, often informally referred to as ammo, is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...
designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions.
An armor-piercing
shellA shell is a payload-carrying projectile, which, as opposed to shot, contains an explosive or other filling, though modern usage includes large solid projectiles previously termed shot...
must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge. Some smaller-
caliberThe term caliber designates the inside diameter of a tube, the diameter of a solid wire or rod, or a measurement of the length of a gun relative to its diameter....
AP shells have an inert filling, or incendiary charge in place of the HE bursting charge. The AP shell is now little used in naval warfare, as modern warships have little or no armor protection, but it remains the preferred round in tank warfare, as it has a greater "first-hit kill" probability than a
high explosive anti-tankIn physics and thermodynamics, heat is the process of energy transfer from one body or system due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body....
(HEAT) round, especially against a target with composite armor, and because of higher
muzzle velocityA gun's muzzle velocity is the speed at which the projectile leaves the muzzle of the gun. Muzzle velocities range from subsonic for some pistols to more than 1,800 m/s for tank guns firing kinetic energy penetrator ammunition. The latter velocity is close to the limit achievable with chemical...
, is also more accurate than a HEAT round.
Armor-piercing
cartridgesA cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim ....
are also available as small arms ammunition, primarily for use as an
anti-matérielAn anti-materiel rifle is a rifle that is designed for use against military equipment rather than against other combatants ....
round.
History
The late 1850s saw the development of the
ironclad warshipAn ironclad was a steam-propelled warship in the later part of the 19th century, protected by iron or steel armor plates. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells. The first ironclad battleship, La Gloire, was launched by the...
, which carried
wrought ironthumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon content, in comparison to steel, and has fibrous inclusions, known as slag. This is what gives it a "grain" resembling wood, which is visible when it is etched...
armor of considerable thickness. This armor was practically immune to both the round cast-iron cannonballs then in use and to the recently-developed explosive shell. The first solution to this problem was effected by
Major Sir W. PalliserMajor Sir William Palliser CB MP was an Irish-born politician and inventor, Member of Parliament for Taunton from 1880 until his death.-Early life:...
, who invented a method of hardening the head of the pointed cast-iron shot. By casting the projectile point downwards and forming the head in an iron mold, the hot metal was suddenly chilled and became intensely
hard (resistant to deformation), while the remainder of the mold, being formed of sand, allowed the metal to cool slowly and the body of the shot to be made
toughToughness, in materials science and metallurgy, is the resistance to fracture of a material when stressed. It is defined as the amount of energy per volume that a material can absorb before rupturing.-Mathematical definition:...
(resistant to shattering).
These chilled iron shots proved very effective against wrought iron armor, but were not serviceable against compound and
steelSteel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten...
armor, which was first introduced in the 1880s. A new departure therefore had to be made, and forged steel rounds with points
hardenedIn metallurgy, hardening describes techniques to increase the hardness of a material. There are five main hardening mechanisms:* Hall-Petch hardening, a hardening that result due to a decrease in grain size.* Cold working, also called strain hardening...
by water took the place of the
Palliser shotPalliser shot was invented by Sir William Palliser and hence its name. It was an early British armour-piercing artillery projectile, intended to pierce the armour protection of warships being developed in the mid-late 1800s.-History:...
. At first, these forged-steel rounds were made of ordinary carbon steel, but as armor improved in quality, the projectiles followed suit.
During the 1890s and subsequently,
cementedThe cementation process is an obsolete technique for making steel by carburization of iron. Unlike modern steelmaking it increased the amount of carbon in the iron. It was apparently developed before the 17th century.-Origins:...
steel armor became commonplace, initially only on the thicker armor of warships. To combat this, the projectile was formed of steel - forged or cast - containing both
nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
and
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odourless, tasteless, and malleable...
. Another change was the introduction of a soft metal cap over the point of the shell.
First World War Era
Shot and shell used prior to and during
World War IWorld War I , also known as the First World War, the Great War, and the War to End All Wars, was a global military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Triple Entente and the Triple Alliance...
were generally cast from special
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odourless, tasteless, and malleable...
(stainless) steel that was melted in pots. They were forged into shape afterward and then thoroughly
annealedAnnealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the re-crystallization temperature and maintaining a suitable temperature,...
, the core bored at the rear and the exterior turned up in a
latheA metal lathe or metalworking lathe is a large class of lathes designed for precisely machining relatively hard materials. They were originally designed to machine metals; however, with the advent of plastics and other materials, and with their inherent versatility, they are used in a wide range of...
. The projectiles were finished in a similar manner to others described above. The final, or
temperingTempering is a heat treatment technique for metals, alloys and glass. In steels, tempering is done to "toughen" the metal by transforming brittle martensite or bainite into a combination of ferrite and cementite. Precipitation hardening alloys, like many grades of aluminum and superalloys, are...
treatment, which gave the required hardness/toughness profile (differential hardening) to the projectile body, was a closely guarded secret.
The rear cavity of these projectiles was capable of receiving a small bursting charge of about 2% of the weight of the complete projectile; when this is used, the projectile is called a shell, not a shot. The HE filling of the shell, whether fuzed or unfuzed, had a tendency to explode on striking armor in excess of its ability to perforate.
Second World War
During WWII, projectiles used highly alloyed steels containing
nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
-chromium-
molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The free element, which is a silvery metal, has the sixth-highest melting point of any element. It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys...
, although in Germany, this had to be changed to a
siliconSilicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon...
-
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
-chromium-based alloy when those grades became scarce. The latter alloy, although able to be hardened to the same level, was more brittle and had a tendency to shatter on striking highly sloped armor. The shattered shot lowered penetration, or resulted in total penetration failure; for armor-piercing high-explosive (APHE) projectiles, this could result in premature detonation of the HE filling. Highly advanced and precise methods of differentially hardening the projectile were developed during this period, especially by the German armament industry. The resulting projectiles gradually change from high hardness (low toughness) at the head to high toughness (low hardness) at the rear and were much less likely to fail on impact.
APHE shells for tank guns, although used by most forces of this period, were not used by the British. The only British APHE projectile was the
Shell AP, Mk1 for the
2 pdr anti-tank gunThe Ordnance QF 2-pounder was a 40 mm British anti-tank and vehicle-mounted gun, employed in the Second World War. It was actively used in the Battle of France, and during the North Africa campaign...
and this was dropped as it was found that the fuze tended to separate from the body during penetration. Even when the fuze didn’t separate and the system functioned correctly, damage to the interior was little different from the solid shot, and so did not warrant the additional time and cost of producing a shell version. APHE projectiles of this period used a bursting charge of about 1-3% of the weight of the complete projectile, the filling detonated by a rear mounted delay fuze. The explosive used in APHE projectiles needs to be highly insensitive to shock to prevent premature detonation. The US forces normally used the explosive
Explosive DDunnite, also known as Explosive D or ammonium picrate, is an explosive developed by Major Dunn in 1906. Ammonium picrate is a salt formed by reacting picric acid and ammonia.It was used extensively by the United States Navy during World War I....
, otherwise known as ammonium picrate, for this purpose. Other combatant forces of the period used various explosives, suitability desensitized (usually by the use of waxes mixed with the explosive).
Due to the increase in armor thickness during the conflict, the projectiles’ impact velocity had to be increased to ensure perforation. At these higher velocities, the hardened tip of the shot or shell has to be protected from the initial impact shock, or risk shattering. To raise the impact velocity and stop the shattering, they were initially fitted with soft steel penetrating caps. The best performance penetrating caps were not very aerodynamic, so an additional ballistic cap was later fitted to reduce drag. The resulting projectile types were given the names "Armor-Piercing Capped (APC)" and "Armor-Piercing Capped Ballistic Capped (
APCBCThe APCBC is a type of armor piercing shell introduced in WWII.The APCBC munition type was an evolutionary development of the early war APC , itself an evolution of the more basic AP and APHE shell types...
)".
Early WWII-era uncapped AP projectiles fired from high-velocity guns were able to penetrate about twice their caliber at close range (100 m). At longer ranges (500-1,000 m), this dropped 1.5-1.1 calibers due to the poor ballistic shape and higher drag of the smaller-diameter early projectiles. Later in the conflict, APCBC fired at close range (100 m) from large-caliber, high-velocity guns (75-128 mm) were able to penetrate a much greater thickness of armor in relation to their caliber (2.5 times) and also a greater thickness (2-1.75 times) at longer ranges (1,500-2,000 m).
Armor-piercing shot
Armor-piercing "shot" for cannons tend to combine some form of incendiary capability with that of armor-penetration. The incendiary compound is normally contained between the cap and penetrating nose, within a hollow at the rear, or a combination of both. If the projectile also uses a
tracerTracer ammunition are special bullets that are modified to accept a small pyrotechnic charge in their base. Ignited upon firing, the composition burns very brightly, making the projectile visible to the naked eye...
, the rear cavity is often used to house the tracer compound. For larger-caliber projectiles, the tracer may instead be contained within an extension of the rear sealing plug. Common abbreviations for solid (non-composite/hardcore) cannon-fired shot are; AP, AP-T, API and API-T; where T stands for "tracer" and I for "incendiary"
Armor-piercing shells
Armor-piercing shells in the classic form are not common in modern guns, though they may be found in the larger (40-57 mm) weapons, especially those of Russian- or Soviet-era descent. Modern guns instead fire semi-armor-piercing high-explosive (SAPHE) shells, which have less anti-armor capability, but far greater anti-materiel/personnel effects. The modern SAPHE projectiles still have a ballistic cap, hardened body and base fuze, but tend to have a far thinner body material and higher explosive content (4-15%). Common abbreviations for modern AP and SAP shells are: HEI(BF), SAPHE, SAPHEI and SAPHEI-T.
Most modern active protection systems (APS) are unlikely to be able to defeat full-caliber AP rounds fired from a large-caliber tank gun. The APS can defeat the two most common anti-armor projectiles in use today:
HEATIn physics and thermodynamics, heat is the process of energy transfer from one body or system due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body....
and
APFSDSA kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....
. The defeat of HEAT projectiles is accomplished through damage/detonation of the HE filling or damage to the shaped charge liner and/or fuzing system, and defeat of
APFSDSA kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....
projectiles is accomplished by inducing yaw/pitch and/or fracturing of the rod. Due to the AP shot/shell's high mass, rigidity, short overall length, and thick body, they are hardly affected by the defeat methods employed by APS systems (fragmentation warheads or projected plates).
Armor-piercing ammunition
Armor-piercing ammunition is used to penetrate hardened armored targets such as ballistic vests, vehicle armor,
concreteConcrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, aggregate , water, and chemical admixtures...
,
tankA tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility and tactical offensive and defensive capabilities...
s, and other defenses, depending on the
caliberThe term caliber designates the inside diameter of a tube, the diameter of a solid wire or rod, or a measurement of the length of a gun relative to its diameter....
of the firearms. Armor-piercing ammunition consists of a penetrator constructed of hardened
steelSteel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten...
,
tungsten carbideTungsten carbide, WC is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
, or
depleted uraniumDepleted uranium is uranium primarily composed of the isotope uranium-238 . Natural uranium is about 99.27 percent U-238, 0.72 percent U-235, and 0.0055 percent U-234. U-235 is used for fission in nuclear reactors and nuclear weapons. Uranium is enriched in U-235 by separating the isotopes by mass...
, enclosed within a softer jacket, such as
copperCopper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
or
aluminiumAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
. Armor-piercing ammunition can range from
rifleA rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...
- and pistol-caliber rounds all the way up to
tankA tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility and tactical offensive and defensive capabilities...
rounds.
Rifle and pistol
roundsA cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim ....
are usually built around a penetrator of
hardened steelThe term hardened steel is often used for a medium or high carbon steel that has been given the heat treatments of quenching followed by tempering. The quenching results in the formation of metastable Martensite, the fraction of which is reduced to the desired amount during tempering. This is the...
or
tungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite...
. Aircraft and tank rounds sometimes use a core of
depleted uraniumDepleted uranium is uranium primarily composed of the isotope uranium-238 . Natural uranium is about 99.27 percent U-238, 0.72 percent U-235, and 0.0055 percent U-234. U-235 is used for fission in nuclear reactors and nuclear weapons. Uranium is enriched in U-235 by separating the isotopes by mass...
. The penetrator is a pointed mass of high-density material that is designed to retain its shape and carry the maximum possible amount of energy as deeply as possible into the target. Depleted-uranium penetrators have the advantage of being
pyrophoricA pyrophoric substance will ignite spontaneously; that is, its autoignition temperature is below room temperature. Examples are iron sulfide and many reactive metals including uranium, when powdered or sliced thinly. Pyrophoric materials are often water reactive as well and will ignite when they...
and self-sharpening on impact, resulting in intense heat and energy focused on a minimal area of the target's armor. Some rounds also use
explosiveAn explosive material is a substance that either is chemically or otherwise energetically unstable or produces a sudden expansion of the material after initiation, usually accompanied by the production of heat and large changes in pressure . This event is called the explosion...
or
incendiaryIncendiary weapons, Incendiary devices or incendiary bombs are bombs designed to start fires or destroy sensitive equipment using materials such as napalm, thermite, chlorine trifluoride, or white phosphorus.According to the...
tips to aid in the penetration of thicker armor.
High Explosive Incendiary/Armor Piercing AmmunitionHigh Explosive Incendiary/Armor Piercing Ammunition is a form of shell which combines both an armour piercing capability and a high explosive effect. In this respect it is a modern version of armour piercing shell...
combines a tungsten carbide penetrator with an incendiary and explosive tip.
Rifle armor-piercing ammunition generally carries its hardened penetrator within a
copperCopper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
or
cupronickelCupronickel or Coppernickel is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Cupronickel is highly resistant to corrosion in seawater, because its electrode potential is adjusted to be neutral with regard to seawater...
jacket, similar to the jacket which would surround
leadLead is a main-group element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air...
in a conventional projectile. Upon impact on a hard target, the copper case is destroyed, but the penetrator continues its motion and penetrates the target. Armor-piercing ammunition for pistols has also been developed and uses a design similar to the rifle ammunition.
The entire projectile is not normally made of the same material as the penetrator because the physical characteristics that make a good penetrator (i.e. extremely tough, hard metal) make the material equally harmful to the barrel of the gun firing the cartridge.
Contrary to popular belief,
TeflonIn chemistry, polytetrafluoroethylene is a synthetic fluoropolymer of tetrafluoroethylene which finds numerous applications. PTFE is most well known by the DuPont brand name Teflon....
or other coatings on a bullet do not help themselves to penetrate more deeply.
Teflon coated bulletTeflon-coated bullets are handgun bullets that have been covered with a coating of Teflon to reduce barrel wear. Molybdenum disulfide is also sometimes used as a coating.-History:...
s are designed purely to help reduce the wear on the barrel as a result of firing hardened projectiles. Teflon-coating bullets is a trend that has largely faded, in part because of laws resulting from this misconception.
Specific AP round examples
| Round |
Projectile |
Weight |
| M2 |
.30-06 SpringfieldThe .30-06 Springfield cartridge or 7.62 x 63 mm in metric notation, was introduced to the United States Army in 1906 and standardized, used until the 1960s and early 1970s. It replaced the .30-03, 6 mm Lee Navy and .30 US Army...
|
163 grain |
| M61 |
7.62x51mm NATO |
150.5 grain |
| FN P80 |
7.62x51mm NATO |
150 grain |
| AP485 |
.338 Lapua Magnum |
248 grain |
| M995 |
5.56x45mm NATO5.56x45mm NATO is a rifle cartridge developed in the United States and originally chambered in the M16 rifle. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries. It is derived from, but not identical to, the .223 Remington cartridge...
|
52 grain |
S.m.K.Also: Patrone SmK 7.92x57 mm MauserThe K bullet is a 7.92x57 mm Mauser caliber armor-piercing bullet which has a tool steel core and which was designed to be fired from a standard Mauser rifle. It was used by the German infantry against the first British tanks in World War I...
|
7.92x57 mm Mauser |
178.25 grain |
See also
- Kinetic energy penetrator
A kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....
- Multipurpose anti-materiel projectile
The Raufoss Mk.211 is a .50 caliber BMG multipurpose anti-materiel projectile originally developed by the Norwegian company NAMMO Raufoss AS under the model name NM140 MP. It is commonly referred to as simply multipurpose or Raufoss. The "Mk.211" name comes from the nomenclature "Mk.211 Mod 0"...
- Panzergranate 39
Panzergranate 39 or Pzgr. 39 was a German armor-piercing shell used during World War II. It was manufactured in various different calibers and was the most common anti-tank shell used in German tank and antitank guns of 50 to 88 mm calibers....
External links