AT4


The AT4 is an 84-mm unguided, portable, single-shot recoilless smoothbore anti-tank weapon built in Sweden by Saab Bofors Dynamics. Saab has had considerable sales success with the AT4, making it one of the most common light anti-tank weapons in the world.
The AT4 is intended to give infantry units a means to destroy or disable armoured vehicles and fortifications, although it is generally ineffective against current modern main battle tanks. The launcher and projectile are manufactured prepacked and issued as a single unit of ammunition, with the launcher discarded after a single use.

Development

The AT4 is a development of the 74-mm Pansarskott m/68, adopted by the Swedish Army in the late 1960s. Like the m/68, the AT4 was designed by Förenade Fabriksverken and manufactured at their facility at Zakrisdal, Karlstad, Sweden. FFV began research in a replacement for the m/68 in 1976, deliberately designing an individual anti-armor weapon that would not be able to defeat the heavy armour protection of MBTs in frontal engagements, believing that to be counterproductive. The AT4 was designed as a weapon to engage medium to light armoured vehicles from any direction, MBTs from the sides or rear, and as an assault weapon against buildings and fortifications. FFV also had the design goal of a weapon that was simple to use, rugged, and far more accurate than previous individual antiarmor weapons against moving targets. Another key requirement was that the AT4 not only be able to penetrate armour, but also have a devastating beyond-armour effect after penetration. FFV and the Swedish Army began the first evaluation firings of the prototype AT4s in the spring of 1981 with 100 tested by early 1982.
Even before the AT4 had been adopted by Sweden, it was entered into a US Army competition for a new anti-tank weapon mandated by Congress in 1982 when the FGR-17 Viper failed as a replacement for the M72 LAW. Six weapons were tested in 1983 by the US Army: the British LAW 80, the German Armbrust, the French APILAS, the Norwegian M72E4, the US Viper and the Swedish AT4. The US Army reported to Congress in November 1983 that the FFV AT4 came the closest to meeting all the major requirements established to replace the M72 LAW, with the Armbrust coming in second.
Though very impressed with the simplicity and durability of the tested version of the AT4, the US Army saw some room for improvement, specifically the addition of rear and front bumpers on the launch tube and changes to the sights and slings. After these changes, the AT4 was adopted by the US Army as the Lightweight Multipurpose Weapon M136. The Swedish Army also recognized these improvements and subsequently adopted the Americanized version of the AT4 as the Pansarskott m/86, with the addition of a forward folding hand grip to help steady the AT4 when being aimed and fired. The forward folding grip is the only difference between the AT4 adopted by Sweden and the US Army version.
Due to the urban combat conditions that US military forces faced regularly during the Iraq War, the US Army Close Combat Systems manager in charge of purchases of the AT4 suspended orders for the standard version of the AT4 and US military forces are now only ordering the AT4 CS version.

Operation

The AT4 may be considered a disposable, low-cost alternative to a Carl Gustaf recoilless rifle. The AT4 took many of its design features from the Carl Gustaf, which operates on the principle of a recoilless weapon, where the forward inertia of the projectile is balanced by the inertia of propellant gases ejecting from the rear of the barrel. But unlike the Carl Gustaf, which uses a heavier and more expensive steel tube with rifling, the disposable AT4 design greatly reduces manufacturing costs by using a reinforced smoothbore fiberglass outer tube. Being a disposable gun also allows for lighter and cheaper construction. In a single-use disposable gun, the barrel only needs to be able to contain a single pressure spike when firing, when it can be disposed of, even if it is ruined, burnt-out and strained, unlike traditional guns which are required to survive many pressure spikes without failure and thus need to be strongly overbuilt and made of heat-proof materials. Pressures are also kept quite low compared to many traditional guns. This lightweight and thin barrel and low pressure, combined with the almost complete lack of recoil, means that relatively large projectiles can be utilised, which would otherwise be impossible in a man-portable weapon.
In the system originally developed by FFV for the Carl Gustaf, a plastic blowout plug is placed at the center rear of the shell casing containing the projectile and propellant, which itself is enclosed in the AT4 outer tube. When the gases build up to the correct pressure level, the blowout plug disintegrates, allowing the proper amount of gases to be vented to the rear, balancing the propellant gases pushing the projectile forward.
The AT4 uses a unique method developed earlier by FFV and adopted for the AT4: the spring-loaded firing rod is located down the side of the outer tube, with the firing pin at the rear of the tube. When released, the firing pin strikes a primer located in the side of the casing's rim.
The disadvantage of the recoilless design is that it creates a large back blast area behind the weapon, which can cause severe burns and overpressure injuries to friendly personnel in the vicinity of the user and sometimes even to the users themselves, especially in confined spaces. The back blast may also reveal the user's position to the enemy. The problem of back blast was solved with the AT4-CS version, specially designed for urban warfare. This version uses a saltwater countermass in the rear of the launcher to absorb the back blast; the resulting spray captures and dramatically slows down the pressure wave, allowing troops to fire from enclosed areas. The AT4-CS version also reduced its muzzle velocity from the original 290 m/s to 220 m/s as part of its effort to be user-safe in a confined space, making the AT4-CS version more difficult to use as the drop is more pronounced. The effectiveness of the HEAT warhead is not dependent on speed.
To fire, the gunner first removes the safety pin located at the rear of the tube, which unblocks the firing rod. He then takes a firing position ensuring that no one is present in the back blast area. If firing from the prone position, he must also place his legs well to the side to avoid burning himself. Then the gunner moves back the front and rear sight covers, allowing the sights to pop up into their firing positions. The AT4 has iron sights that were originally developed for the cancelled Viper, and are similar in concept and use to those on assault rifles. He then removes the first of two safeties by moving the firing rod cocking lever forward and then over the top to the right side. The gunner takes aim, while at the same time holding down the red safety lever located in front of the cocking lever, and then fires by pressing forward the red firing button with his right thumb. Both the red safety lever and the firing button must be pressed down at the same time to fire the AT4. The red firing button has a similar resistance to the trigger pull of a rifle, so the gunner does not have to jab at the firing button, which could throw his aim off.
and an AT4.
After firing, the AT4 is discarded. Unlike the heavier Carl Gustaf, the AT4 outer tube is built to take the stress of just one firing; it is not reusable and cannot be reloaded.
The AT4 can mount an optical night sight on a removable fixture. In US military use, the launcher can be fitted with the AN/PAQ-4C, AN/PEQ-2, or the AN/PAS-13 night sights.
The AT4 requires little training and is quite simple to use, making it suitable for general issue. However, as the cost of each launcher makes regular live-fire training very expensive, practice versions exist that are identical in operation but fire reloadable 9×19mm or 20mm tracer ammunition. Both practice cartridges are unique to their respective weapons, with their trajectory matched to that of the live round. The 20mm version also has a recoilless weapon effect with the same high noise and back blast as the AT4 firing and is favoured by the Swedish army because of the added realism of the back blast as compared to the "plonk" sound of the 9mm round.

Specifications

There are several different projectiles for the AT4. Note that because the AT4 is a one-shot weapon, projectiles are preloaded into the launcher tubes.
;HEAT
;HEDP 502
;HP
;AST
;ER
;HE

Variants

;M136 AT4
;AT8
;AT12-T

Operators