Armour-piercing ammunition

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The first major application of armour-piercing projectiles was to defeat the thick armour carried on many warships and cause damage to their lightly armoured interiors. From the 1920s onwards, armour-piercing weapons were required for anti-tank warfare. AP rounds smaller than 20 mm are intended for lightly armoured targets such as body armour, bulletproof glass, and lightly armoured vehicles.

As tank armour improved during World War II, anti-vehicle rounds began to use a smaller but dense penetrating body within a larger shell, firing at very high muzzle velocity. Modern penetrators are long rods of dense material like tungsten or depleted uranium (DU) that further improve the terminal ballistics.

History

The late 1850s saw the development of the

The first solution to this problem was effected by Major Sir W. Palliser, who, with the Palliser shot, invented a method of hardening the head of the pointed cast-iron shot.^[2] 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 through a Martensite phase transformation), 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 tough^[2] (resistant to shattering).

These chilled iron shots proved very effective against wrought iron armour but were not serviceable against compound and steel armour,^[2] which was first introduced in the 1880s. A new departure, therefore, had to be made, and forged steel rounds with points hardened by water took the place of the Palliser shot. At first, these forged-steel rounds were made of ordinary carbon steel, but as armour improved in quality, the projectiles followed suit.^[2]

During the 1890s and subsequently,

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 high-explosive filling of the shell, whether fuzed or unfuzed, had a tendency to explode on striking armour in excess of its ability to perforate.[2]

World War II

During World War II, projectiles used highly alloyed steels containing nickel-chromium-molybdenum, although in Germany, this had to be changed to a silicon-manganese-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 armour. The shattered shot lowered penetration, or resulted in total penetration failure; for armour-piercing high-explosive (APHE) projectiles, this could result in premature detonation of the high-explosive filling. Advanced and precise methods of differentially hardening a projectile were developed during this period, especially by the German armament industry. The resulting projectiles change gradually 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 for tank use in this period was the Shell AP, Mk1 for the

Cap configurations

Name	Schematic	Description
AP – Armour-piercing		No cap
APC – Armour-piercing capped		Armour-piercing cap
APBC – Armour-piercing ballistic capped		Ballistic cap
APCBC – Armour-piercing capped ballistic capped		Ballistic cap

Cap suffixes (C, BC, CBC) are traditionally only applied to AP, SAP, APHE and SAPHE-type projectiles (see below) configured with caps, for example "APHEBC" (armour-piercing high explosive ballistic capped), though sometimes the HE-suffix on capped APHE and SAPHE projectiles get omitted (example: APHECBC > APCBC). If fitted with a tracer, a "-T" suffix is added (APC-T).

Penetrator and filling

Projectile configurations (incomplete list)

Name	Schematic	Description
AP – Armour-piercing[a] SAP – Semi-armour-piercing[b]		Solid or hollowed steel body
APHE – Armour-piercing high-explosive[c] SAPHE – Semi-armour-piercing high-explosive[d]		Hollowed steel body   Explosive charge
APCR – Armour-piercing composite rigid		High-density hard material   Deformable metal
APDS – Armour-piercing discarding sabot		Spin-stabilized penetrator   Sabot
APFSDS – Armour-piercing fin-stabilized discarding sabot		Fin-stabilized penetrator   Sabot

Armour-piercing non-solid shells

An armour-piercing shell must withstand the shock of punching through

The primary shell types for modern anti-tank warfare are discarding-sabot kinetic energy penetrators, such as APDS. Full-calibre armour-piercing shells are no longer the primary method of conducting anti-tank warfare. They are still in use in artillery above 50 mm calibre, but the tendency is to use semi-armour-piercing high-explosive (SAPHE) shells, which have less anti-armour capability but far greater anti-materiel and anti-personnel effects. These still have ballistic caps, hardened bodies and base fuzes, but tend to have far thinner body material and much higher explosive contents (4–15%).

Common terms (and acronyms) for modern armour-piercing and semi-armour-piercing shells are:

• HEI-BF – High-explosive incendiary (base fuze)
• SAPHE – Semi-armour-piercing high-explosive
• SAPHEI – Semi-armour-piercing high-explosive incendiary
• SAPHEI-T – Semi-armour-piercing high-explosive incendiary tracer

HEAT

High-explosive anti-tank (HEAT) shells are a type of shaped charge used to defeat armoured vehicles. They are very efficient at defeating plain steel armour but less so against later composite and reactive armour. The effectiveness of such shells is independent of velocity, and hence the range: it is as effective at 1000 metres as at 100 metres. This is because HEAT shells do not lose penetrating ability over distance. The speed can even be zero in the case where a soldier places a magnetic mine onto a tank's armour plate. A HEAT charge is most effective when detonated at a certain, optimal distance in front of a target and HEAT shells are usually distinguished by a long, thin nose probe protruding in front of the rest of the shell and detonating it at a correct distance, e.g., PIAT bomb. HEAT shells are less effective when spun, as when fired from a rifled gun.

HEAT shells were developed during World War II as a

Armour-piercing solid shot for cannons may be simple, or composite, solid projectiles but tend to also combine some form of incendiary capability with that of armour-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 tracer, the rear cavity is often used to house the tracer compound. For larger-calibre 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". More complex, composite projectiles containing explosives and other ballistic devices tend to be referred to as armour-piercing shells.

AP

Early WWII-era uncapped armour-piercing (AP) projectiles fired from high-velocity guns were able to penetrate about twice their calibre at close range (100 m). At longer ranges (500–1,000 m), this dropped 1.5–1.1 calibres due to the poor ballistic shape and higher drag of the smaller-diameter early projectiles. In January 1942 a process was developed by Arthur E. Schnell^[6] for 20 mm and 37 mm armour piercing rounds to press bar steel under 500 tons of pressure that made more even "flow-lines" on the tapered nose of the projectile, which allowed the shell to follow a more direct nose first path to the armour target. Later in the conflict, APCBC fired at close range (100 m) from large-calibre, high-velocity guns (75–128 mm) were able to penetrate a much greater thickness of armour in relation to their calibre (2.5 times) and also a greater thickness (2–1.75 times) at longer ranges (1,500–2,000 m).

In an effort to gain better aerodynamics, AP rounds were given

Armour-piercing, capped projectiles had been developed in the early 1900s, and were in service with both the British and German fleets during World War I. The shells generally consisted of a

Further information:

high-carbon steel

in AP shot). They act as low-cost ammunition with worse penetration characteristics to contemporary high carbon steel projectiles.

This section needs expansion. You can help by adding to it. (November 2023)

APCR/HVAP

Armour-piercing composite rigid (APCR) in British

aerodynamic drag

. Tungsten compounds such as tungsten carbide were used in small quantities of inhomogeneous and discarded sabot round, but that element was in short supply in most places. Most APCR projectiles are shaped like the standard APCBC round (although some of the German Pzgr. 40 and some Soviet designs resemble a stubby arrow), but the projectile is lighter: up to half the weight of a standard AP round of the same calibre. The lighter weight allows a higher muzzle velocity. The kinetic energy of the round is concentrated in the core and hence on a smaller impact area, improving the penetration of the target armour. To prevent shattering on impact, a shock-buffering cap is placed between the core and the outer ballistic shell as with APC rounds. However, because the round is lighter but still the same overall size it has poorer ballistic qualities, and loses velocity and accuracy at longer ranges. The APCR was superseded by the APDS, which dispensed with the outer light alloy shell once the round had left the barrel. The concept of a heavy, small-diameter penetrator encased in light metal was later employed in small-arms armour-piercing incendiary and HEIAP rounds.

APCNR/APSV

Main article: Squeeze bore

Further information: Littlejohn adaptor, 2.8 cm sPzB 41, and 7.5 cm Pak 41

Armour-piercing, composite non-rigid (APCNR) in British

Gerlich principle. This projectile design is very similar to the APCR-design - featuring a high-density core within a shell of soft iron or another alloy - but with the addition of soft metal flanges or studs along the outer projectile wall to increase the projectile diameter to a higher caliber. This caliber is the initial full-bore caliber, but the outer shell is deformed as it passes through the taper. Flanges or studs are swaged down in the tapered section so that as it leaves the muzzle the projectile has a smaller overall cross-section.^[8]

This gives it better flight characteristics with a higher sectional density, and the projectile retains velocity better at longer ranges than an undeformed shell of the same weight. As with the APCR, the kinetic energy of the round is concentrated at the core of impact. The initial velocity of the round is greatly increased by the decrease of barrel cross-sectional area toward the muzzle, resulting in a commensurate increase in velocity of the expanding propellant gases.

The Germans deployed their initial design as a light anti-tank weapon, 2,8 cm schwere Panzerbüchse 41, early in World War II, and followed by the 4.2 cm Pak 41 and 7.5 cm Pak 41. Although HE rounds were also put into service, they weighed only 93 grams and had low effectiveness.^[9] The German taper was a fixed part of the barrel.

In contrast, the British used the Littlejohn squeeze-bore adaptor, which could be attached or removed as necessary. The adaptor extended the usefulness of armoured cars and light tanks, which could not be upgraded with any gun larger than the QF 2 pdr. Although a full range of shells and shot could be used, changing an adaptor during a battle is usually impractical.

The APCNR was superseded by the APDS design which was compatible with non-tapered barrels.

APDS

Main article: armour-piercing discarding sabot

An important armour-piercing development was the armour-piercing discarding sabot (APDS). An early version was developed by engineers working for the French Edgar Brandt company, and was fielded in two calibres (75 mm/57 mm for the 75 mm Mle1897/33 anti-tank gun, 37 mm/25 mm for several 37 mm gun types) just before the French-German armistice of 1940.^[10] The Edgar Brandt engineers, having been evacuated to the United Kingdom, joined ongoing APDS development efforts there, culminating in significant improvements to the concept and its realization. The APDS projectile type was further developed in the United Kingdom between 1941 and 1944 by L. Permutter and S. W. Coppock, two designers with the Armaments Research Department. In mid-1944 the APDS projectile was first introduced into service for the UK's QF 6-pdr anti-tank gun and later in September 1944 for the QF-17 pdr anti-tank gun.^[11] The idea was to use a stronger and denser penetrator material with smaller size and hence less drag, to allow increased impact velocity and armour penetration.

The armour-piercing concept calls for more penetration capability than the target's armour thickness. 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. Generally, the penetration capability of an armour-piercing round increases with the projectile's kinetic energy and also with concentration of that energy in a small area. Thus, an efficient means of achieving increased penetrating power is increased velocity for the projectile. However, projectile impact against armour at higher velocity causes greater levels of shock. Materials have characteristic maximum levels of shock capacity, beyond which they may shatter, or otherwise disintegrate. At relatively high impact velocities, steel is no longer an adequate material for armour-piercing rounds. Tungsten and tungsten alloys are suitable for use in even higher-velocity armour-piercing rounds, due to their very high shock tolerance and shatter resistance, and to their high melting and boiling temperatures. They also have very high density. Aircraft and tank rounds sometimes use a core of

explosive or incendiary tips to aid in the penetration of thicker armour. High explosive incendiary/armour piercing ammunition combines a tungsten carbide

penetrator with an incendiary and explosive tip.

Energy is concentrated by using a reduced-diameter tungsten shot, surrounded by a lightweight outer carrier, the sabot (a French word for a wooden shoe). This combination allows the firing of a smaller diameter (thus lower mass/aerodynamic resistance/penetration resistance) projectile with a larger area of expanding-propellant "push", thus a greater propelling force and resulting kinetic energy. Once outside the barrel, the sabot is stripped off by a combination of centrifugal force and aerodynamic force, giving the shot low drag in flight. For a given calibre, the use of APDS ammunition can effectively double the anti-tank performance of a gun.

APFSDS

Main article: Armour-piercing fin-stabilized discarding sabot

Armour-piercing fin-stabilized discarding sabot (APFSDS) in English

air-resistance, thus increasing velocity, while still having a long body to retain great mass by length, meaning more kinetic energy. Velocity and kinetic energy both dictates how much range and penetration the projectile will have. This long thin shape also has increased sectional density

, in turn increasing penetration potential.

Large calibre (105+ mm) APFSDS projectiles are usually fired from

D-10T.^[12]

However, as such guns have been taken out of service since the early 2000s onwards, rifled APFSDS mainly exist for small- to medium-calibre (under 60 mm) weapon systems, as such mainly fire conventional full-calibre ammunition and thus need rifling.

APFSDS projectiles are usually made from high-density metal alloys, such as

pyrophoric and may become opportunistically incendiary, especially as the round shears past the armour exposing non-oxidized metal, but both the metal's fragments and dust contaminate the battlefield with toxic hazards. The less toxic WHAs are preferred in most countries except the US and Russia.^{[citation needed}

]

Aerial bombs

Further information: Bunker buster

Armour-piercing bombs dropped by aircraft were used during World War II against capital and other armoured ships. Among the bombs used by the Imperial Japanese Navy in the attack on Pearl Harbor were 800 kg (1,800 lb) armour-piercing bombs, modified from 41-centimeter (16.1 in) naval shells,^[13] which succeeded in sinking the battleship USS Arizona.^[14] The Luftwaffe's PC 1400 armour-piercing bomb and the derived Fritz X precision-guided bomb were able to penetrate 130 mm (5.1 in) of armour.^[15] The Luftwaffe also developed a series of bombs propelled by rockets to assist in penetrating the armour of ships and similar targets.^[16]

Small arms

Main article:

Armour-piercing bullet

Armour-piercing rifle and pistol

FN 5.7mm round, is inherently capable at piercing armour, being of a small calibre and very high velocity. 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.^{[citation needed}

]

Defense

Most modern active protection systems (APS) are unlikely to be able to defeat full-calibre AP rounds fired from a large-calibre anti-tank gun, because of the high mass of the shot, its rigidity, short overall length, and thick body. The APS uses fragmentation warheads or projected plates, and both are designed to defeat the two most common anti-armour projectiles in use today: HEAT and kinetic energy penetrator. Defeating HEAT projectiles can occur by damaging or detonating their explosive filling, or by damaging a shaped charge liner or fuzing system. Defeating kinetic energy projectiles can occur by inducing changes in yaw or pitch or by fracturing the rod.

See also

• Panzergranate 39
• Raufoss Mk 211

Notes

1. High-carbon steel
   solid shot.
2. Mild steel
   solid shot – low-cost ammunition with worse penetration characteristics to contemporary high-carbon steel projectiles.
3. ^ Type with a small explosive charge for added post-penetration damage. Designated APHEI if filled with a high explosive incendiary charge.
4. ^ Type with a large explosive charge for major post-penetration damage at the cost of penetration. Designated SAPHEI if filled with a high explosive incendiary charge.
5. ^ In case of the british Littlejohn adaptor, ammunition was designated as armour-piercing, super-velocity (APSV).

References

1. ^ "Armour-piercing projectile". Encyclopedia Britannica. Retrieved 2021-02-19.
2. ^ ^{a b c d e f g h} Seton-Karr, Henry (1911). "Ammunition" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. pp. 864–875.
3. ^ ^{a b} Bonnier Corporation (February 1945). "The Bazookas Grandfather". Popular Science. Bonnier Corporation. p. 66.
4. ^ Donald R. Kennedy,'History of the Shaped Charge Effect, The First 100 Years – USA – 1983', Defense Technology Support Services Publication, 1983
5. ^ Ian Hogg, Grenades and Mortars' Weapons Book #37, 1974, Ballantine Books
6. ^ Western Hills Press, Cheviot Ohio Page 3-B May 30th 1968
7. ISBN 9781107150140
   .
8. ^ ^{a b} Popular Science, December 1944, pg 126 illustration at bottom of page on working principle of APCBC type shell
9. ISBN 978-5-17-015302-2
   .
10. ^ "Shells and Grenades". Old Town, Hemel Hempstead: The Museum of Technology. Archived from the original on 16 October 2010. Retrieved 2010-10-23.
11. ^ Jason Rahman (February 2008). "The 17-Pounder". Avalanche Press. Archived from the original on 9 November 2010. Retrieved 2010-10-23.
12. ^ Ogorkiewicz, Richard M (1991). Technology of tanks. Jane's Information Group. p. 76.
13. OCLC 2365447
    .
14. ^ Hone, Thomas C. (December 1977), "The Destruction of the Battle Line at Pearl Harbor", Proceedings, vol. 103, no. 12, United States Naval Institute, pp. 56–57
15. ^ Fitzsimons, Bernard, ed. "Fritz-X", in The Illustrated Encyclopedia of 20th Century Weapons and Warfare (London: Phoebus, 1978), Volume 10, p. 1037.
16. ^ "Rocket-Propelled Bomb PC 1000 Rs". Catalog Of Enemy Ordnance Material. Office of the Chief of Ordnance. 1 August 1945. p. 316.

Bibliography

• Okun, Nathan F. (1989). "Face Hardened Armor". Warship International. XXVI (3): 262–284.
  ISSN 0043-0374
  .
• Hogg, Ian V. (1985). The Illustrated Encyclopedia of Ammunition. Apple Press.

External links

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