- "Wrist fired grenade that will detonate on targets."
- — Create-A-Class description.
It works similar as regular grenades but explodes on impact if an enemy is hit. Otherwise, it will bounce off surfaces, but will explode after a very fast delay compared to standard fragmentation grenades. It can be unlocked in the customize class menu. The grenade can not be cooked and the action may be cancelled by pressing the weapon-swap button/scrolling mouse wheel. Another added benefit is that the trajectory of impact is shown on the HUD which can occasionally be useful. In the main campaign levels, only Fragmentation grenades may be fired, but in various Strike Force missions, Semtex grenades may also be fired (in this case the HUD displays Semtex grenades rather than the XM31 launcher).
XM31 grenades are part of the recommended loadout for all future levels. They cannot be refilled with the Ammo Pickup Perk; they can only be refilled with ammo boxes, which means that the players should use these grenades only against large groups of enemies or against ASDs, CLAWs and sentry turrets. In Fallen Angel, Section and Harper use a rope from the XM31.