The US Army announced its award of a US$494.35 million contract to SAAB to provide AT4 Confined Space Tandem Warhead (CSTW) Individual Shoulder Fired recoilless weapon to address its requirement for the Individual Assault Munition (IAM).
The IAM program is intended to replace three single-use individual shoulder-fired weapons currently in service with one weapon which is effective against a range of targets. These targets include defeating light armour, earth and timber bunders, double reinforced concrete, adobe and brick walls.
According to the Army requirements it must also have an effective range of not less than 500 meters and have substantial after-penetration effects. Its physical characteristics included a weight not to exceed 20 lbs (9.09 kg) and length not greater than 40 inches (1.6 m).
IAM will substitute for the M72 Light Anti-Armour Weapon (LAAW), the M141 Bunker Defeat Munition, and current M136 AT4. Replacing these with a one munition will offer tactical, logistics, training and other benefits while also providing one weapon that can address these multiple threats.
The M72 was initially fielded in the 1960s and had the advantages of a compact 630 mm (24.8 inch) carry length and 2.5 kg (5.5lb) weight in the A1 to A3 versions (increasing to 3.6 kg (7.9 lb) in the later A7 to A7 models).
Its limitations were its 200-meter effective range and target effect largely a result of its 66mm warhead diameter. Nammo, the developer, did introduce a number of improvements to the weapon over its life. The company also proposed its own candidate for the IAM which was nor selected.
The M136 BDM (Bunker Defeat Munition) is a single-use derivative of the reloadable SMAW originally fielded by the US Marines as a bunker-buster. It used a dual-purpose high-explosive warhead. It weighs 7.1 kg (15.7 lb) with a collapsed (carry) length of 810 mm (32 inch).
The AT4 was developed by FFV of Sweden, later SAAB, and introduced in the mid1980s. It was adopted by US Forces as the M136.
The design essentially draws from the 84mm Carl Gustav reloadable recoilless gun utilizing the munition in a single-use launch tube. As a result, the AT4 has been able to be offered in a number of versions with different warheads derived from the Carl Gustav.
These include the CS (Confined Space) version which can be safety employed from inside a building and the TW (Tandem Warhead). The CS TW is the version to be provided as the XM919 IAW.
The TW employs two HEAT warheads which detonate in succession greatly increasing both penetration and behind armour effects. The TW is designed to counter protection systems intended to defeat single warheads.
The AT4’s projectile velocity (it achieves 250 meters in one second) makes it accurate even against moving targets and provides and effective range of 600 meters.
An advantage of the selection of this AT4 version for the IAM will be that soldier’s will already be familiar with the weapon, its operation, and use as these functions remain common to the current M136.
In addition, the Army requirement for a subcalibre training version (the XM922) can be adapted from the similar AT4 system.
The award is “an Indefinite Delivery, Indefinite Quantity (IDIQ) contract”. It allows the service to place individual orders over the next five years for quantities of the IAM.
A company release stated, “Saab’s new addition to the battle-tested AT4 family combines the capability of multiple existing shoulder-launched munitions while reducing soldier load, training complexity and logistics burden.”
by Stephen W. Miller
