Saab’s latest weapon is like a high-tech bazooka

The Carl Gustaf is a type of recoilless rifle, and the weapon and the round inside of it can share information with one another. Here's how.
The Carl Gustaf M4. Saab

On May 10, Sweden’s military announced it would be purchasing a new kind of ammunition for a weapon it already owns: the Carl Gustaf Recoilless Rifle. While bearing a superficial resemblance to the bazooka anti-tank gun used by the United States in World War II, and common among plastic toy soldiers to this day, the Carl Gustaf belongs to a tradition of recoilless rifles—those are hollow tubes for large-caliber explosives that have spiral grooves in the barrel to enhance the accuracy of the rounds fired. Unlike typical rifles, recoilless rifles can be big enough to mount on vehicles, and fire explosives much larger than bullets. Like bazookas, recoilless rifles are open in the back, allowing exhaust from the fired explosive to vent directly backwards, so shots can be fired without producing any recoil.

Made by Swedish defense giant Saab, the Carl Gustaf is a venerable weapon, a sophisticated and durable rifled tube that first entered military service in 1948. With this latest type of ammunition, called High Explosive (HE) 448, the rifle can pull off a new trick: It can automatically program the round with information from the rifle’s fire control software, promising faster, more accurate firepower on the move. In other words, the weapon and its ammunition are able to communicate with one another while the round is loaded in the weapon.

The Carl Gustaf M4 pairs its rifled metal tube with a sophisticated set of sensors and computers, and the explosive ammunition that goes inside. Weighing roughly 15 pounds and stretching about 3 feet in length, the body of the weapon has been shortened and lightened from previous versions. On the weapon, the Fire Control Device, FCD 558, includes sensors for temperature and air pressure, which help it calibrate how the round will travel through the air in the exact atmospheric conditions at the moment of firing.

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“Using a toggle on the FCD, the gunner is able to choose either direct fire or air burst, and this information is electronically communicated to the fuze inside the round before firing,” says a Saab release. (Saab has also produced a short video on the weapon.) “The gunner uses the same toggle to enter the range to target. Equipped with information on range, round type, propellant temperature and the required mode, the FCD’s ballistic computer calculates the best possible trajectory to achieve success.”

That lets the person firing the weapon determine if an airburst or a direct impact is the better way to attack a target, and trust the weapon to calculate as much of that information as possible. With an airburst, the HE 448 detonates above or near a target, letting the fragments and blast travel through the air above a group of enemies, a machine gun nest, or even next to the light armor on the side of a vehicle. 

“The HE 448 round provides the FCD 558 with the exact information on round type and propellant temperature and combines this with target distance entered by the operator to determine the best trajectory. This means that Carl-Gustaf operators will be able to quickly configure a chambered round and so increase their operational effectiveness,” said Saab in an announcement of the order.

While the most straightforward way to operate the weapon is to fire directly at a vehicle within range, that’s not the only option, and this is where programmability matters. If the enemy is within range but exposed, like behind a small wall or hiding in a trench, programming an air burst from a high explosive round above the enemy position will be deadlier than a direct shot. That’s where the fire control, range finding, and mode selection matters most.

High explosives are just one kind of ammunition that can be fired with the weapon. A 2017 brochure for the weapon lists 10 rounds available at the time, divided by function. These include anti-personnel rounds that produce smokescreens or blinding light, anti-armor, and versatile or anti-building rounds. The HE 448 is designed as a specific replacement for the HE 441 RS, an anti-personnel round, designed to incapacitate and kill people caught in its blast.

This makes the weapon useful for ambushing transport vehicles, as well as soldiers fighting in open terrain, hiding behind cover, or nestled into foxholes. The Carl Gustaf, with the HE 448, has a range of over 4,200 feet, or at least 4/5ths of a mile.

At the same time in the 1940s that Saab first developed the Carl Gustaf, the United States was experimenting with a range of larger recoilless rifles for its own forces. In 1945, Popular Science covered the 57-MM as a “Kickless Cannon for GI’s.” The 57-mm is a large two-person anti-tank weapon that “can be fired as accurately as the [M1] Garand” standard infantry rifle, hurling a 2.75 pound shell 2.5 miles. A 75-mm version was developed around the same time, with a 90-mm version fielded by 1960.

Some recoilless rifles saw use in World War II, with the Carl Gustaf first introduced into service in 1948. By the Korean War, recoilless rifles became a standard part of how infantry fought against tanks, and in “New GI WeaponsPopular Science paired coverage of the 75-mm with the improved “Super Bazooka” as anti-tank tools of the infantry. Mounting recoilless rifles on jeeps made them more mobile while also making them bigger targets for enemy fire. The ability to attack armor while moving into position and then out of range is a durable feature of recoilless rifles, which offer a lighter alternative to heavier artillery. 

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Unlike many Cold War weapons, the Carl Gustaf has remained in service since its creation, though modern versions can carry and use sensors that were unimaginable when it was first created in the 1940s. Today, the Carl Gustaf is fielded by a range of militaries, including Ukraine, which in March received a shipment of 100 recoilless rifles and 2000 rounds from Canada. A Ukrainian brigade commander has even claimed that a Carl Gustaf was used to destroy a modern T-90M Russian tank, the kind of vehicle that should be beyond the scope of most Gustaf ammunition.

In its announcement, Saab said the first deliveries of the HE 448 to Sweden’s military will take place in 2023 and continue through 2025. Whether or not the fire computer and programmable round live up to its expectations in combat will have to wait to see how and when the new rounds perform once delivered. In the meantime, the weapon is one of many modern tools that shifts some of the precision targeting to the launcher, letting the actual projectile fly a plotted course, until it meets an explosive end.