Video: Nammo’s new supercavitating ammunition “swims through water”

The Norwegian/Finnish aerospace and defense group Nammo has released video footage of its 30 mm Swimmer (APFSDS-T MK 258 Mod 1) supercavitating ammunition that swims through water.

The company says the projectile was developed in cooperation with the US Navy.

According to Nammo’s design engineer Jan Hasslid, the Swimmer is unique because of the combination of powerful armor penetration and its ability to swim straight through water.

This effect has until now been considered impossible to achieve by ammunition fired from air through water. As demonstrated by a number of popular science TV programs, traditional ammunition is either stopped or deflected when it hits water. In a worst case scenario, a projectile could hit the surface, bounce off and hit something else.

Thanks to the design effort for the kinetic energy penetrator originally developed for the Norwegian Army, and perfected by Nammo in combination with US Navy supercavitation concepts, the Swimmer avoids the ricochet in water problem through the use of a supercavitation nose design. This means that the projectile creates a bubble of steam around itself big enough to pass through, substantially reducing the friction that stops traditional ammunition.

This enables the Swimmer to be used in defense of either ships or coastal areas against submerged and surface mines, small underwater vehicles, torpedoes and even small fast attack crafts that might be concealed by waves. This is valuable not only for naval vessels, but also for land vehicles defending harbors, bridges or other key locations.

Nammo says it has recently signed agreements with the US Army and the US Navy under which both services will adopt Nammo’s 30 mm APFSDS-T MK 258 Mod 1, or Swimmer, for use from a multitude of platforms, including the US Army’s latest addition, the Stryker variant known as Dragoon.

As explained by the company, the Swimmer round falls into the category of sub-caliber kinetic energy penetrators. These can most easily be described as arrows made out of very heavy materials that use the force of the impact rather than explosives to punch through armor. Traveling at speeds of more than 1 km per second, the energy generated by the impact melts the armor of the vehicle into a fluid and the arrow “swims” through the armored side of the vehicle. In the case of the Swimmer, the force of the arrow is sufficient to defeat anything except main battle tanks.