The M320, a 40mm grenade launcher, is the replacement to all M203 series of grenade launchers on M16 Rifles and M4 Carbines. An interoperable system, it attaches under the barrel of the rifle or carbine and can convert to a stand-alone weapon.

The integral day/night sighting system, unrestricted breech mechanism, and double-action firing trigger deliver superior overmatch capabilities. Located on the side of the launcher, the new sighting system design lessens interference with rifle and carbine sights, reduces attaching operations to one action, and eliminates the need to re-zero after reattaching to a weapon.

The M320 barrel opens to the side, allows for an unrestricted breech enabling the firing of all standard U.S. 40mm low-velocity ammunition as well as longer-than standard ammunition. The new pistol grip design eliminates the need to use the magazine as a hand grip. If the weapon misfires, the operator can pull the trigger again, compared with the M203, which requires cycling of the breech to re-cock the firing pin and pulling the trigger again. With the advancement of composite materials, the latest in lightweight material.