AT4 – Light Anti-Tank Weapon

The AT4 (also variously AT-4, AT4 CS, AT4-CS, or AT-4CS) is an 84-mm unguided, portable, single-shot recoilless smoothbore weapon built in Sweden by Saab Bofors Dynamics (previously Bofors Anti-Armour Systems). Saab has had considerable sales success with the AT4, making it one of the most common light anti-tank weapons in the world.

The designation “CS” represents “confined space” referring to the propellant charge being designed to operate effectively within buildings in an urban environment. It is intended to give infantry units a means to destroy or disable armored vehicles and fortifications, although it is not generally sufficient to defeat a modern main battle tank (MBT). The launcher and projectile are manufactured prepacked and issued as a single unit of ammunition with the launcher discarded after a single use.

The AT4 is a development of the 74-mm Pansarskott m/68 (Miniman), adopted by the Swedish Army in the late 1960s. Like the m/68, the AT4 was designed by Försvarets Fabriksverk (FFV) 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 armor protection of MBTs (main battle tanks) in frontal engagements, believing that to be counterproductive.

The AT4 was designed as a weapon to engage medium to light armored 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 armor, 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.

The AT4 may be considered a disposable, low-cost alternative to a Carl Gustav recoilless rifle. The AT4 took many of its design features from the Carl Gustav, 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 Gustav, 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.

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 side of the tube. When released, the firing pin strikes a primer located in the side of the casing’s rim. Additionally, as the shell casing absorbs the majority of the firing stresses, the launch tube can be designed to be very lightweight as it does not have to contend with the extreme pressures found in traditional cannons.

The problem of back blast has been recently solved with the AT4-CS (Confined Space) 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. It should be noted that 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 less effective.

The AT4 can mount an optical night sight on a removable fixture. In U.S. 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 exists which are identical in operation but fire reloadable 9mm or 20mm tracer ammunition.

Specification

Length: 101.6 cm (40 in.)
Weight: 6.7 kg (14.77 pounds)
Bore diameter: 84 mm
Maximum effective range: 300 meters (328 yards), although it has been used in excess of 500 meters (547 yards) for area fire.
Penetration: 400 mm (15.7 inches) of rolled homogeneous armor (RHA) (also see below)
Time of flight (to 250 meters, or 273 yards): less than 1 second
Muzzle velocity: 285 meters (950 ft) per second
Operating temperature: -40 to +60°C (-40 to +140°F)
Ammunition: Fin-stabilized projectile with HEAT warhead