New anti-tank round punches through high-tech explosive armor

Saab has developed a new anti-tank round that's designed to take on the modern high-tech armor of the 21st century. Built for Saab's Carl-Gustaf 84-mm (3.31-in) recoilless rifle system, the HEAT 758 munition can even defeat modern reactive armor.

People whose knowledge of armor and the weapons to penetrate it come from popular entertainment tend to underestimate the complex battle between offense and defense that has played out over the past century – especially when it comes to developing handheld weapons that can take on main battle tanks. It's a lot more than large, fiery explosions hitting slabs of recalcitrant metal.

When the first tanks emerged during the First World War, they were protected by riveted plates of mild steel that could be penetrated by a high-powered rifle. By the Second World War, the steel alloys had improved in composition, metal fabrication methods made armor more homogeneous, and the thickness was increased to create much tougher plating. This was improved even more by learning how to slope the armor to deflect incoming shells and dissipate the impact.

This was countered by new anti-armored weapons like the German Panzerfaust and Panzerschreck, the American. Bazooka, and the British PIAT, all of which used shaped charges to concentrate the explosive force of the warhead into a jet of white-hot metal that burned through thick plating. This counter was counter-countered then counter-counter-countered as composite armors were invented that consisted of steel, ceramics, and composites, which then later to contend with high-velocity darts made of depleted uranium.

One particularly effective advance was Explosive Reactive Armor (ERA), where the tank's hull is covered with steel boxes filled with high explosives. These boxes are designed to detonate if hit by a shaped charge, generating a counter-explosion that disrupts and deflects the incoming projectile or blast.

This reactive armor has become increasingly sophisticated, so Saab and other defense contractors have had to become increasingly sophisticated as well.

Demonstrated on May 7 in Karlskoga, Sweden , the HEAT 758 is that latest round made for the Cold War-vintage Carl-Gustaf family of recoilless rifles. It's specifically engineered to take on heavy armored vehicles protected by modern reactive armor, including the Kontakt-1, Kontakt-5, and Relikt systems.

The HEAT 758 is what is known as a tandem-charge anti-tank munition consisting of two stages. Earlier versions of such tandem-charge rounds defeat the reactive armor by having the first charge hit the explosive box, setting it off. This allows the second stage to penetrate to the now unprotected steel plate and blast through it with a shaped charge.

It's a sound concept, but that first explosion can be counterproductive as it interferes with the secondary main charge jet. The HEAT 758 tries to overcome this with a Non-Initiating Precursor (NIP) in the second stage that takes advantage of a weakness of reactive armor.

Contrary to popular belief, explosives are not easy to set off. Dynamite won't go BOOM if you drop it, you can toss gelignite like it's putty, and I've actually seen TNT burn in a camp fire. To make any of these explode, you need a chain of increasingly sensitive explosives added to the main charge leading back to a detonator to set off the big show.

This is important when it comes to reactive armor because having it sitting on a tank means it has to be sensitive enough to explode if hit by hostile fire, but not if the vehicle happens to rear-end a Honda, which would make people talk. What the HEAT 758 does is to exploit the sweet spot by hitting the reactive armor hard enough to penetrate it and open up a path for the shaped charge, but not hard enough to detonate it.

According to Saab, this is the result of using AI to run 50,000 digital simulations of how the HEAT 758 hits its target. In addition, the round uses Firebolt technology, which employs a digital communication link between the munition, the Carl-Gustaf M4 launcher, and the Fire Control Device 558 to retrieve data about the specific ammunition type and propellant temperature to calculate the optimal ballistic trajectory for maximum effect.

The HEAT 758 can penetrate Rolled Homogeneous Armor up to 100 mm thick at an effective range of up to 700 m (766 yd) with a muzzle velocity of 255 m/s (570 mph). Each round weighs about 7 kg (16 lb) and is less than 1 m (39 in) long, with a sleeve made of carbon composites and a titanium barrel liner.

According to the company, the HEAT 758 is already under production for an undisclosed customer.

"This round is our response to developments on the battlefield where reactive explosive armor has become a major problem for regular munitions trying to defeat armored vehicles," said Michael Höglund, head of Saab’s business unit Ground Combat. "HEAT 758 is an example of how Saab continues to generate ever more capable products while decreasing the armored vehicle threat to the operator."

Source: Saab