A modular hand grenade that can be modified to increase explosive power by connecting other grenades may be next on the Corps’ list for a future grenade.

The scalable hand grenade the Corps is looking at is manufactured by Nammo — the makers of the Corps’ single-shot light anti-tank rocket launcher known as the M72 LAW.

The grenade produces little fragmentation and relies on over-pressurization to produce casualties or knock out enemy forces hiding in enclosed rooms, Pat Woellhof, the director of Marine Corps operations for Nammo, told Marine Corps Times at the 2019 Modern Day Marine expo.

It’s known as an offensive hand grenade due to the small amount of fragmentation that disburses from the grenade upon explosion. The Corps calls it the Mk 21 Mod 0, and Woellhof says the Corps doesn’t have an offensive hand grenade in its arsenal.

Instead, the Corps relies on a defense grenade known as the M67 fragmentation grenade. That grenade has fragmentation that creates an effective casualty radius of 15 meters upon explosion.

There are some drawbacks to relying strictly on a defensive grenade, Woellhof said. With a defensive hand grenade, “you can’t throw it far enough to get outside the fragmentation,” Woellhof said.

Marines who cleared dense urban terrain in bloody fights in the Iraqi cities Fallujah and Haditha are still carrying pieces frag and shrapnel in their bodies from their own grenades, Woellhof explained.

Marines clearing rooms with defensive grenades may have also inadvertently caused civilian casualties, Woellhof said.

“If you throw an M67 into a room it doesn’t discriminate."

Nammo’s offensive grenade can limit collateral damage. The device is modular, so a Marine can increase or decrease explosive power by adding grenade bodies. The explosive power of the grenade depends on how many grenade bodies are connected together.

A base grenade will cause concussions if a Marine tosses it into a room.

“And you know, they’ll wake up with a bad hangover,” Woellhof said.

Two connected base grenades will provide 261 grains of explosives and “will kill anything in a room,” Woellhof explained. Three grenade bases will produce 391 grains of explosives and can be used to destroy structures, he said.

The Corps is “interested and pursuing” the MK21 Mod 0 grenade but nothing has been signed or approved at this time, according to Maj. Joshua Benson, a Marine spokesman.