AT-4 Single-shot anti-tank recoilless rifle

Zarvan · Dec 11, 2016

Developed from the less successful and effective Miniman, the AT-4 is one of the world's premier disposable anti-tank weapons

Country of origin Sweden
Entered service 1986
Weapon caliber 84 mm
Projectile 84 x 462 mm
Weight (loaded) 6.7 kg
Projectile weight ?
Warhead type HEAT
Length 1 016 mm
Muzzle velocity 285 m/s
Sighting range 500 m
Range of effective fire against tanks 300 m
Range of effective fire against area targets 500 m
Armor penetration 400 mm

The AT-4 is a man-portable, disposable, single-shot anti-tank weapon, developed by FFV (now SAAB-Bofors) in Sweden. The name of the weapon is a play on its 84 mm bore (AT-4 is pronounced as "Eighty-Four"), as well an indication of its role (AT for "anti-tank"). It was and remains one of the world's premier expendable infantry anti-tank weapons. It is also distinct from most other weapons in its class, being a recoilless gun rather than a rocket launcher, though many sources still mistakenly identify it as the latter. The AT-4 is also often assumed to simply be a disposable version of the Carl Gustav M2, but the only major attribute their ammunition shares is the same bore.

The effort to develop what would become the AT-4 began with an early 1970s analysis of (then) contemporary Soviet armor. The findings were bleak; the Miniman disposable anti-tank weapon first fielded in 1968 was found to be inadequate against armor like that on the T-62, while the T-72 was a tough nut to crack even with a flank shot, and almost invulnerable to the Miniman over its frontal arc. The Swedish Army had realized, in essence, that they had fielded the Miniman just in time for its obsolescence, and a successor was called-for in 1974.

Work on the new weapon began in 1976 at FFV, the same company that had developed the Miniman. They basically scaled-up the 74 mm Miniman's design, creating an 84 mm variant with an improved projectile and charge, and a largely new type of gun tube. Though these represented radical changes, the first firing AT-4 prototypes were submitted to the Swedish armed forces by the Spring of 1981, and over 100 had been test-fired by the same date in 1982. The AT-4 had also caught the attention of the US Army, who at that time was desperate for a new weapon in this class to replace the 66 mm M72 LAW anti-tank rocket launcher. While the Swedish Army was continuing to evaluate the AT-4 in 1983, it was one of 6 weapons tested by the US Army in the same year, and they surprised many with an announcement in November of 1983 that the AT-4 was formally selected as the LAW's replacement.

Several alterations were made to the AT-4 to suit US Army requirements, which resulted in the M136. In a peculiar reversal of the norm, the US military hurriedly adopted an innovative foreign weapon system, while the Swedish military's testing and evaluation dragged-on for years afterwards. The M136 also impressed the Swedish Army, who requested that FFV incorporate some of its new features into the AT-4 as well. Sweden's evaluation of the AT-4 continued for the next 3 years, before finally being formally adopted as the Pansarskott m/86.

The AT-4's gun tube is long and cylindrical, with numerous external fixtures. The muzzle is surrounded by a thick composite bracket, which in turn is enveloped by an octagonal shock absorber; the venturi is flared, conical, and has an octagonal shock absorber rim as well, though its visibly broader than the muzzle. Numerous brackets are wrapped around the tube, making quick identification by counting them relatively pointless. The shoulder pad on the aft underside has a broad salient shape, and includes a folding wire-frame shoulder rest with a short canvas strap; when extended, the shoulder rest takes-on a delta shape. A long tube covered by a conformal housing (which contains a cable used to fire the weapon) runs from the trigger mechanism to the breech along the top of the tube. The front and rear sights are located on the forward upper right side of the tube, underneath rectangular protective covers which can be slid-away when the sights needs to be raised. A rectangular foregrip is located just behind the muzzle on the underside of the weapon, and is folded against the tube when not in use (some AT-4s were produced without a foregrip). The firing mechanism, safety catch, and cocking lever are on top of the tube in its midsection, just behind the rear sight cover. The AT-4 is usually fitted with a sling, the swivels for which are located on the lower left side between the sight covers, and on the very bottom of the tube just in front of the venturi. Various stencilings and instructional decals are plastered onto the tube. AT-4s may be painted in different colors or camouflage patterns, but are usually solid olive drab in color.

The construction of the AT-4's gun tube is extremely similar to that of most modern disposable anti-tank rocket launchers, but is still able to cope with the overpressure of an 84 mm recoilless round. The tube consists of reinforced fiberglass, with numerous sheet steel and composite brackets. Unlike the Miniman, the bore liner is not metallic, although the venturi is made of aluminum. The shock absorbers on the AT-4 are made of a hard foam rubber material. The sights, trigger mechanisms, and shoulder rest frame are made of steel, while the sight covers, foregrip, and numerous other fixtures are made of plastic. The projectile itself has an aluminum shell, and the fins are probably made of aluminum as well. The AT-4 is rated for operating temperatures of −40 to +60 °C.

The iron sights consist of a front post and a rear peephole, with the range adjustable for 100 m to 500 m, in 50 m increments. Two different peepholes are available for the AT-4; a 2 mm hole for use in broad daylight, and a 7 mm peephole for use at night and in order low-visibility situations. Interestingly similar set of sights are also used on the M141 BDM rocket launcher, probably due to a similar range and trajectory. A variety of optics may also be fitted to the AT-4 by clipping them on, to include night vision optics, infrared optics, and laser aiming devices.

The main body of the projectile is shaped like a generic artillery shell, with a cylindrical body, a finely-tapered conical nose, and a boattail. It has a diameter of 84 mm, a length of 462 mm, and a fin span of 290 mm. The trailing body consists of a metal shaft, enveloped by a spring-loaded assembly containing 6 stabilizer fins that spring into a hexagonal pattern when the projectile leaves the tube. The main body of the projectile is marked with a yellow band, for easy identification of UXO, should the projectile fail to launch and/or detonate properly. The projectile is fired down a smooth bore, and is stabilized solely by drag via its fins when in flight, as it does not rotate. Although the AT-4 is frequently referred-to as a "rocket launcher", the projectile does not contain a rocket motor.

The AT-4 projectile weighs 1.81 kg, and contains 453 g of Octol that force a thin copper charge liner into a jet-like penetrator upon detonation. This charge will penetrate up to 400 mm of RHAe at a 0-degree obliquity, but there is more to the lethality of the warhead than just its penetration. The AT-4 was the first anti-tank munition especially designed to employ enhanced lethality against armored vehicles, through what the manufacturer has termed "Beyond Armor Effects". Using a number of special attributes built into the warhead, the damage caused to the interior of a penetrated armored vehicle and its occupants are dramatically increased, resulting in a significantly greater probability of disabling an armored vehicle. These effects include an instantaneous overpressure of 1 bar above normal (twice the ambient air pressure of the Earth's atmosphere at sea level), greatly increased back-spalling and penetrator spatter, a flash of light over 100 times stronger than sunlight, greatly increased smoke from combustion of the warhead and armor during penetration, and more intense heat than that of a generic shaped charge of similar penetration. Exactly what components of the AT-4's warhead create the Beyond Armor Effects are still highly classified (though observers have noted that it probably has something to do with the charge liner's unusual trumpet-like shape, a focus ring around the front of the liner, or an additional layer of a special aluminum-based alloy bonded to the back of the liner), but as video footage and photographs of AT-4s hitting armored vehicles graphically demonstrate, they are not a marketing overstatement.

The armor penetration figure is not uncontested however, as different sources offer different ratings. For example, some US Army field manuals state the penetration is as little as 356 mm, while others offer a significantly larger 450 mm figure. Some sources even claim that this weapon will penetrate 500 mm of RHAe. The advent of the more powerful AT-4-HP hasn't added any clarification either, with penetration figures ranging from 500 mm to 600 mm. Given that the earlier 74 mm Miniman was rated to penetrate 350 mm RHAe, however, its safe to assume the 84 mm AT-4 is capable of at least 400 mm RHAe penetration.

The AT-4 may be fired from a standing, sitting, kneeling, or prone position, though prone firings are typically forbidden during training. When firing from a prone position, the user must lie at a 45-degree angle off the axis of fire, as being exposed to the backblast at the venturi will result in severe injuries.

To fire the AT-4, the user must first remove the safety pin at the rear of the launch tube, ensure no personnel are in the backblast area, and shoulder the weapon. If the iron sights are to be used, the user must slide the cover for the front sight rearward, slide the cover for the rear sight forward, and flip-up the sights. The cocking lever must then be flipped moved forward, upward, then to the right, then take aim at the target. When the target is in the user's sights, the safety lever must then be held down, and the trigger button pressed-down by the user's thumb; if the cocking lever is not set to the armed position and the safety lever held-down with the trigger is pressed, the trigger will not engage and fire the weapon. The user must also *squeeze* the trigger until it "breaks" (like the trigger on a typical rifle) rather than simply jabbing it, as doing the latter could throw-off the aimpoint. The weapon will then fire, and the tube is discarded; it isn't designed to withstand the stresses of multiple firings, and thus cannot be reloaded.

As the AT-4 is for all intents and purposes a cannon, it should come as no surprise that its backblast is exceptionally powerful. The backblast area has a 90-degree angle, with the danger area within 40 m of the venturi, and the caution area extending 40 m to 100 m behind the venturi. The danger area must be totally clear of personnel, animals, vulnerable equipment, and loose objects prior to firing, while personnel inside the caution area must take cover and protect their ears. The AT-4 must never be fired from inside an enclosed area, as the rebounding backblast will cause significant shock and hearing injuries to any personnel inside said space.

The AT-4 has seen combat in numerous conflicts, to include the Afghan War, the Iraq War, and Operation Serval (the French Intervention in Mali). If the M136 is included, the list is expanded even further, to include every US ground war since Operation Just Cause (the 1989 Invasion of Panama). In several of these wars, the AT-4 proved its worth against armored vehicles of all shapes and sizes, it was able to defeat some structures, and it even proved valuable against unarmored targets such as trucks.

A number of limitations of the AT-4 also became evident in these conflicts. For example, the AT-4's Beyond Armor Effects were quite limited when it was used to engage structures, and the huge backblast was often a serious problem. It became increasingly clear from these events that anti-structure variants and a countermass were required for future conflicts, which resulted in the development of a variety of new variants (see below).

The AT-4's known operators include Argentina, Bosnia and Herzegovina, Brazil, Chile, Colombia, Croatia, Denmark, Estonia, France, Greece, Indonesia, Iraq, Ireland, Latvia, Lebanon, Lithuania, Malaysia, the Netherlands, the Philippines, Poland, Sweden, Taiwan, the UK, the US and Venezuela. This also includes the M136 variant, as publications are relatively vague on which nations operate which (although the M136, specifically, is used by the US, and not the AT-4). According to the SAAB-Bofors webpage on the AT-4 as of late 2016, a total of 15 nations operate this weapon.

As of 2016, over 300, 000 AT-4s have been manufactured, and full-scale production is ongoing.

Designations

Pskott m/86: Swedish Army designation ("Pansarskott m/86").

SRAAW: Irish Defense Forces designation ("Short Range Anti Armor Weapon").

L2A1 ILAW: British Army designation ("Interim Light Anti-tank Weapon").

PVV M/95: Danish Army designation ("Panserværnsvåben 95").

ABL: French Army designation ("Anti Blindé Léger").

Variants

AT-4: Initial production model. It is unclear is these were adopted, as the AT-4s procured by Sweden ended up being modeled after the M136.

M136: US version of the AT-4, with new sights and different ergonomical features. Some of these changes were back-fitted to the AT-4 itself before Sweden adopted it, and it is otherwise identical to the AT-4. Many publications consider the AT-4 and M136 to be the same weapon, which has lead to both often being awkwardly referred to by the catch-all, "M136 AT-4".

AT-4-CS: Adds a saltwater countermass, which tremendously reduces the shock and backblast from firing the AT-4, allowing it to be fired from confined spaces (the "CS" in the designation is short for "Confined Space").

HEDP 502: Replaces the usual HEAT warhead with an HEDP warhead. The new warhead is programmable to detonate at the moment of impact, or just after. When detonating on impact, the blast tears a large hole into the wall of a structure (a "mousehole", as the term goes), which personnel can crawl through, or additional munitions can be fired through to clear more of the building. When detonating after impact, the munition explodes behind the wall it penetrated, causing immense damage to materials and personnel inside. The HEDP 502 warhead also penetrates up to 150 mm RHAe.

AT-4-AST: Anti-structure variant with a tandem HEDP warhead. The first charge of the warhead bores a hole though a thick concrete wall, just wide enough for the second charge to follow through, which then detonates inside the structure with a higher yield and an unfocused blast. An alternate setting causes both charges to detonate simultaneously on impact, to mousehole thick walls.

AT-4-HP: Has an improved shaped charge warhead, capable of penetrating 600 mm RHAe.

AT8: Anti-structure version of the AT-4 for the US Army, with a warhead optimized for destroying hardened structures such as pillboxes. It was ultimately rejected in favor of the M141 BDM, and no other military purchased it either. With the advent of the AT-4-AST, the AT8 has effectively been discontinued.

AT12: 120 mm version for the US Army with a tandem HEAT warhead for defeating explosive reactive armor, and significantly increased range and armor penetration as well. The AT12 program was abandoned due to reduced budgets and shifting strategic priorities after the Cold War, and the design was abandoned.

Similar weapons

ALAC: Extremely similar Brazilian weapon developed by IMBEL. The tube is uncannily similar to that of the AT-4, but the propellant charge and projectile appear to be similar to those used in the Carl Gustav M2 recoilless rifle. The ALAC is gradually replacing the AT-4 in the Brazilian armed forces.

LAW 80: British disposable anti-tank rocket launcher, similar in design and capability to the AT-4. It is highly unusual among modern anti-tank weapons, in that the LAW 80 has a self-loading spotting rifle. Its effective range and armor penetration also far exceed that of the AT-4.

APILAS: French disposable anti-tank rocket launcher, similar to the AT-4. However, the APILAS is a larger-bore weapon, and significantly more powerful than the AT-4.

Armbrust: German disposable anti-tank rocket launcher, with a countermass and a unique tube-sealing mechanism; the sealing mechanism tremendously reduces the flash, smoke, and acoustic report from the launch, while the countermass virtually eliminates the backblast.

MATADOR: International disposable anti-structure rocket launcher with an HEDP warhead. It is basically an oversized, dual-purpose version of the Armbrust, and has a manually-set programmable fuze that causes the warhead to detonate as either a shaped charge, or like a HESH warhead.

M141 BDM: US disposable anti-structure rocket launcher, firing a rocket developed from the ammunition for the Mk.153 SMAW. This rocket has an HEDP warhead with two detonation settings like others of this type, but a unique fuzing system; the fuze automatically selects one of the two settings (detonation on impact or follow-through detonation) based on the force of impact.

PF-89: Chinese disposable anti-tank rocket launcher, similar in form and function to the AT-4.

C90-CR: Spanish disposable anti-tank rocket launcher, with a slightly larger 90 mm bore.

NOTE: The AT-4 should not be confused with the AT-4 Spigot (9K111 Fagot) anti-tank guided missile; the two are unrelated.