Tandem-charge

A tandem-charge weapon is an explosive device or projectile that has two or more stages of detonation. It is effective against reactive armour, which is designed to protect an armoured vehicle (mostly tanks) against anti-tank munitions. The first stage of the weapon is typically a weak charge that either pierces the reactive armour of the target without detonating it leaving a channel through the reactive armour which the HEAT jet of the second warhead may pass unimpeded, or simply detonating the armourplate causing the timing of the counter-explosion to fail. The second detonation from the same projectile (which defines it as a tandem charge) attacks the same location as the first detonation where the reactive armour has been compromised. Since the regular armour plating is often the only defence remaining, the main charge (second detonation) has an increased likelihood of penetrating the armour.

However, tandem-charges are useful only against ERA (explosive reactive armour) types of reactive armour, much less so against the non-explosive reactive armour (NxRA) types, since their inner liner is not explosive itself and thus not expended by the small forward warhead of tandem-charge attack.

The PG-7VR warhead for the RPG-7 rocket launcher and the more modern RPG-29 rocket are examples of tandem charges, but the technology is employed world-wide because they were designed in the Cold War era to counter the reactive armour that was a common feature on Soviet tanks. Examples of missiles that use tandem charges include the BGM-71 TOW, FGM-148 Javelin and the MBT LAW.