Beyond-armour effect
Encyclopedia
Beyond-Armour Effect is a term coined by Försvarets Fabriksverk (FFV), a semi-governmental Swedish defense firm, while developing the AT4
. From the 1980s this phrase was used in its brochures, press releases, weapon instruction manuals and other documentation to denote the post-penetration effect of the AT4's HEAT
anti-armour warhead against the interior and occupants of armoured vehicles.
The phrase now has become more or less standard in modern military terminology.
, man-portable antitank weapons using shaped charge warheads, more commonly known today as HEAT
projectiles, came into widespread use with almost all armies. These warheads have the advantage of not being affected by the projectile's velocity. They penetrate armour by an explosive charge fitted in a liner in the shape of a cone or, more precisely, an ogive
. The liner often is made of a soft metal, such as copper. Burning of this shaped charge turns it into a highly focused stream moving forward at extreme speeds. These warheads also have the same effect as medium and high velocity solid shot armour piercing projectiles: spall
ing on the interior of the armoured vehicle's armoured plate.
A problem with shaped charge warheads is that if the ogive shaped liner is deep, it will have more penetration, that results in a smaller hole, that is less effective inside the armoured vehicle. Research on shaped charge warheads has shown a hole the size of a large coin on the outside of a tank turret, but an inside hole the diameter of pencil lead. If, on the other hand, the ogive is shallow, it will have less penetration, but cause a larger hole on the inside which will result in a massive spalling.
In 1954, during the siege of Dien Bien Phu
, France had dismantled and flown in a number of M-24 Chaffee light tanks. Their thickest armor was only 25.4mm. The Viet Minh's
main infantry antitank weapon was the old World War Two U.S. 2.36-inch bazooka
, captured from Nationalist Chinese forces and supplied by Communist China
. During the siege the French launched counterattacks using the M-24 in support of their infantry. One Chaffee took seven hits from 2.36-inch bazookas and still continued to fight, demonstrating that portable rocket launchers were hardly a flawless tank-killer.
Other examples became evident during the Second Indochina War
. The North Vietnamese and their allied forces in South Vietnam were equipped with two types of light anti-armour weapons. One was the 1950s era B-40 which was a Chinese manufactured version of the Russian RPG-2
and the other was the newer RPG-7
. The RPG-2 had a shallow cone and the RPG-7 a deep cone. The RPG-2 had a maximum penetration against armour of approximately 150mm while the RPG-7 penetration was more than double that of the RPG-2. But to the surprise of the North Vietnamese, the RPG-2, while not effective against heavy tanks, was far more effective than the RPG-7 in killing or wounding the occupants of light armoured vehicles, and in igniting the ammunition storage or the vehicles fuel, including the more modern M113 APC
which U.S. and South Vietnamese forces at that time operated in large numbers. In addition, the B-40 proved more effective than the RPG-7 against non-armoured targets, like the bunkers at fire base camps. There are many stories from U.S. Vietnam veterans of the enemy attacking or ambushing with the dreaded B-40. The U.S. Army also discovered that in combat, that with rare exception more than one hit by the M72 LAW
rocket was required to disable or kill the North Vietnamese PT-76
light tank.
in the late 1970s. The result was the AT4 with a HEAT warhead that had, as the early AT4 brochures stated, a special beyond-armour effect. The designers of the AT4's warhead intended that one hit cause massive damage to the both the interior and occupants of targeted vehicles. FFV has said very little about the design of the AT4's warhead—only its effect. Many defense journalists and military experts have speculated. One clue was a cutaway photo of the AT4's projectile which instead of the standard cone shape liner used by other HEAT warheads, has a unique liner which is trumpet-shaped. Trumpet-shaped liners are believed to be more effective in resisting the counter-blast of reactive armour
tiles, that explode and disrupt the HEAT warhead's particle stream. There has been speculation that the liner in the AT4's HEAT warhead is constructed of a special aluminum alloy, and others have stated it is primarily a copper liner with a secondary liner of aluminum bonded to the back of the copper liner. Cutaway photos of the AT4's HEAT warhead also shows what is referred to as a "focus ring". All public statements to date on that subject is speculation. In tests of the AT4 conducted by the U.S. Army, they concluded that the claims made by FFV regarding the AT4's devastating post-penetration effect were substantially correct.
FFV claims that besides the effect of the massive spalling and fragmentation on the occupants of the armoured vehicle, which is standard for all HEAT warheads to a degree, the massive overpressure and intense heat will cause ammunition and more importantly the armoured vehicle's diesel fuel to ignite. The intense light effect will blind any occupants for at least seven minutes, in addition to the obscuring effect of the dense smoke created by the AT4's HEAT warhead.
AT4
The AT4 is an 84-mm unguided, portable, single-shot recoilless smoothbore weapon built in Sweden by Saab Bofors Dynamics...
. From the 1980s this phrase was used in its brochures, press releases, weapon instruction manuals and other documentation to denote the post-penetration effect of the AT4's HEAT
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
anti-armour warhead against the interior and occupants of armoured vehicles.
The phrase now has become more or less standard in modern military terminology.
History
During World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, man-portable antitank weapons using shaped charge warheads, more commonly known today as HEAT
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
projectiles, came into widespread use with almost all armies. These warheads have the advantage of not being affected by the projectile's velocity. They penetrate armour by an explosive charge fitted in a liner in the shape of a cone or, more precisely, an ogive
Ogive
An ogive is the roundly tapered end of a two-dimensional or three-dimensional object.-Applied physical science and engineering:In ballistics or aerodynamics, an ogive is a pointed, curved surface mainly used to form the approximately streamlined nose of a bullet or other projectile.The traditional...
. The liner often is made of a soft metal, such as copper. Burning of this shaped charge turns it into a highly focused stream moving forward at extreme speeds. These warheads also have the same effect as medium and high velocity solid shot armour piercing projectiles: spall
Spall
Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...
ing on the interior of the armoured vehicle's armoured plate.
A problem with shaped charge warheads is that if the ogive shaped liner is deep, it will have more penetration, that results in a smaller hole, that is less effective inside the armoured vehicle. Research on shaped charge warheads has shown a hole the size of a large coin on the outside of a tank turret, but an inside hole the diameter of pencil lead. If, on the other hand, the ogive is shallow, it will have less penetration, but cause a larger hole on the inside which will result in a massive spalling.
In 1954, during the siege of Dien Bien Phu
Battle of Dien Bien Phu
The Battle of Dien Bien Phu was the climactic confrontation of the First Indochina War between the French Union's French Far East Expeditionary Corps and Viet Minh communist revolutionaries. The battle occurred between March and May 1954 and culminated in a comprehensive French defeat that...
, France had dismantled and flown in a number of M-24 Chaffee light tanks. Their thickest armor was only 25.4mm. The Viet Minh's
Viet Minh
Việt Minh was a national independence coalition formed at Pac Bo on May 19, 1941. The Việt Minh initially formed to seek independence for Vietnam from the French Empire. When the Japanese occupation began, the Việt Minh opposed Japan with support from the United States and the Republic of China...
main infantry antitank weapon was the old World War Two U.S. 2.36-inch bazooka
Bazooka
Bazooka is the common name for a man-portable recoilless rocket antitank weapon, widely fielded by the U.S. Army. Also referred to as the "Stovepipe", the innovative bazooka was amongst the first-generation of rocket propelled anti-tank weapons used in infantry combat...
, captured from Nationalist Chinese forces and supplied by Communist China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
. During the siege the French launched counterattacks using the M-24 in support of their infantry. One Chaffee took seven hits from 2.36-inch bazookas and still continued to fight, demonstrating that portable rocket launchers were hardly a flawless tank-killer.
Other examples became evident during the Second Indochina War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
. The North Vietnamese and their allied forces in South Vietnam were equipped with two types of light anti-armour weapons. One was the 1950s era B-40 which was a Chinese manufactured version of the Russian RPG-2
RPG-2
The RPG-2 was the first rocket-propelled grenade launcher designed in the Soviet Union.-Development:The RPG-2 , was a man-portable, shoulder-launched rocket-propelled grenade anti-armor weapon...
and the other was the newer RPG-7
RPG-7
The RPG-7 is a widely-produced, portable, unguided, shoulder-launched, anti-tank rocket-propelled grenade launcher. Originally the RPG-7 and its predecessor, the RPG-2, were designed by the Soviet Union, and now manufactured by the Bazalt company...
. The RPG-2 had a shallow cone and the RPG-7 a deep cone. The RPG-2 had a maximum penetration against armour of approximately 150mm while the RPG-7 penetration was more than double that of the RPG-2. But to the surprise of the North Vietnamese, the RPG-2, while not effective against heavy tanks, was far more effective than the RPG-7 in killing or wounding the occupants of light armoured vehicles, and in igniting the ammunition storage or the vehicles fuel, including the more modern M113 APC
M113 armored personnel carrier
The M113 is a fully tracked armored personnel carrier that has formed the backbone of the United States Army's mechanized infantry units from the time of its first fielding in Vietnam in April 1962. The M113 was the most widely used armored vehicle of the U.S...
which U.S. and South Vietnamese forces at that time operated in large numbers. In addition, the B-40 proved more effective than the RPG-7 against non-armoured targets, like the bunkers at fire base camps. There are many stories from U.S. Vietnam veterans of the enemy attacking or ambushing with the dreaded B-40. The U.S. Army also discovered that in combat, that with rare exception more than one hit by the M72 LAW
M72 LAW
The M72 LAW is a portable one-shot 66 mm unguided anti-tank weapon, designed in the United States by Paul V. Choate, Charles B. Weeks, and Frank A. Spinale et al...
rocket was required to disable or kill the North Vietnamese PT-76
PT-76
The PT-76 is a Soviet amphibious light tank which was introduced in the early 1950s and soon became the standard reconnaissance tank of the Soviet Army and the other Warsaw Pact armed forces. It was widely exported to other friendly states, like India, Iraq, North Korea and North Vietnam. Overall,...
light tank.
Development
The combat record of light anti-armour weapons was studied by the engineers at FFV working on a replacement for the Pansarskott m/68Miniman antitank weapon
The Miniman is a disposable single-shot 74-mm unguided anti-tank smooth bore recoilless weapon, designed in Sweden by Försvarets Fabriksverk and became operational in 1968. The Miniman is delivered with the HEAT projectile pre-loaded launch tube...
in the late 1970s. The result was the AT4 with a HEAT warhead that had, as the early AT4 brochures stated, a special beyond-armour effect. The designers of the AT4's warhead intended that one hit cause massive damage to the both the interior and occupants of targeted vehicles. FFV has said very little about the design of the AT4's warhead—only its effect. Many defense journalists and military experts have speculated. One clue was a cutaway photo of the AT4's projectile which instead of the standard cone shape liner used by other HEAT warheads, has a unique liner which is trumpet-shaped. Trumpet-shaped liners are believed to be more effective in resisting the counter-blast of reactive armour
Reactive armour
Reactive armour is a type of vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected. It is most effective in protecting against shaped charges and specially hardened long rod penetrators...
tiles, that explode and disrupt the HEAT warhead's particle stream. There has been speculation that the liner in the AT4's HEAT warhead is constructed of a special aluminum alloy, and others have stated it is primarily a copper liner with a secondary liner of aluminum bonded to the back of the copper liner. Cutaway photos of the AT4's HEAT warhead also shows what is referred to as a "focus ring". All public statements to date on that subject is speculation. In tests of the AT4 conducted by the U.S. Army, they concluded that the claims made by FFV regarding the AT4's devastating post-penetration effect were substantially correct.
Description
As described by FFV in their first AT4 brochure in 1983, the beyond-armour effect had five distinctive characteristics upon penetration of an armoured vehicle:- A massive overpressure inside the vehicle of approximately 1 barBar (unit)The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
over normal.
- Secondary fragments from the warhead itself due to a larger entry hole, plus more extensive spalling than caused by HEAT warheads of similar diameter.
- An intense light that is 100 times brighter than sunlight.
- Generation of dense smoke in the armoured vehicle's interior.
- Extensive heat is generated inside the armoured vehicle.
FFV claims that besides the effect of the massive spalling and fragmentation on the occupants of the armoured vehicle, which is standard for all HEAT warheads to a degree, the massive overpressure and intense heat will cause ammunition and more importantly the armoured vehicle's diesel fuel to ignite. The intense light effect will blind any occupants for at least seven minutes, in addition to the obscuring effect of the dense smoke created by the AT4's HEAT warhead.