The AT4 (or AT-4) is a portable one-shot anti-tank weapon built in Sweden by Saab Bofors Dynamics (previously Bofors Anti Armour Systems). Saab have had considerable sales success with the AT4, making it one of the most common light anti-tank weapons in the world. It is intended to give infantry units a means to destroy or disable armored vehicles and fortifications they may encounter (though it is not generally sufficient to defeat a modern main battle tank). The projectile is carried pre-packed in the launcher, which is non-reloadable and discarded after use.
The AT4 operates on the principle of a «recoilless weapon,» meaning that the forward inertia of the projectile is balanced by the mass of propellant gases ejecting out the rear of the barrel. Since the weapon generates almost no recoil, a relatively large projectile can be fired which would otherwise be impossible in a man-portable weapon. Additionally, since the barrel does not have to contend with the extreme pressures found in traditional guns, it can be designed to be very lightweight. The disadvantage of this design is that it creates a large «back-blast» area behind the weapon which can cause severe burns and pressure injuries. This makes it difficult to employ in confined areas.
To fire, the user must first ensure that no friendly troops or equipment are present in the backblast area. If firing from the prone, (i.e. lying on his stomach) he must also place his legs well to the side to avoid burning himself. He then disengages two safeties, cocks a mechanical firing pin and presses a trigger button. Aiming is accomplished via non-adjustable iron sights, which are concealed beneath sliding covers for transport. Alternatively, the weapon can carry an optical night-sight on a removable mount. The AT4 requires little training and is quite simple to utilize, making it suitable for general issue. Because the expensive unit cost is prohibitive to regular live-fire training, a practice version exists which is identical in operation but fires (reloadable) 9mm tracers.
* Length: 101.6 cm (40 in.)
* Weight: 6.7 kg (14.75 pounds)
* Bore diameter: 84 mm
* Maximum effective range: 300 metres (984.3 feet)
* Penetration: 400 mm of rolled homogeneous armour (also see below)
* Time of Flight (to 250 metres): less than 1 second
* Muzzle velocity: 285 metres (950 feet) per second
* Operating temperature: -40 to +60° C (-40 to +140° F)
* Ammunition: Fin-stabilized projectile with shaped charge warhead
There are several different projectiles for the AT4. Note that since the AT4 is a one-shot weapon, these projectiles are preloaded.
HEAT (High Explosive Anti Tank)
The AT4 HEAT is a low-trajectory, low-dispersion weapon that can penetrate up to 420 mm of armour.
HEDP (High Explosive Dual Purpose)
For use with bunkers and buildings. The projectile can be set to detonate on impact or with a delayed detonation.
HP (High Penetration)
Extra high penetration ability. Can penetrate 500 to 600 mm armour.
The AT4 CS (Confined Space) is a variant of the AT4 specially designed for urban warfare.
The regular AT4 can be extremely dangerous to fire from confined spaces due to the extreme increase in pressure. The back flame can also bounce back at the soldier if there is a wall or another solid object within 15 metres of the breech. The «CS» version utilizes a liquid countermass ejected from the rear upon firing, which neutralizes some of the backblast. While the CS is considerably safer than the regular AT4, there have still been reports of soldiers fainting when firing the AT4 CS from confined spaces.
* Ireland, designated SRAAW in the Irish Defence Forces.
* Sweden, designated Pansarskott m/86 (AT4 CS) and used by Swedish urban warfare units.
* Republic of China (Taiwan)
* United Kingdom, designated L2A1 (ILAW) (AT4 CS with high penetration warhead), used by the British Army.
* United States, designated M136 AT4 in USMC and United States Army service.