The M320 is a limited-use grenade launcher being developed by Heckler & Koch to replace the M203 grenade launcher. It fires the same 40mm underbarrel grenades, but uses a breach-loading mechanism as opposed to the free-sliding barrel of the M203. The weapon can be used either as an underbarrel attachment on many assault rifles, including the M16/M4 series of rifles, or as a standalone weapon. It is a variant of the AG-36 grenade launcher used on the L85A2 and G36 assault rifles.
In the prototype phase, it was known as the XM320, and was seen on the XM8 assault rifle.