M320 Grenade Launcher Module (GLM) is the U.S. military's designation for a new single-shot 40 mm grenade launcher system to replace the M203 for the U.S. Army, while other services initially kept using the older M203. The M320 uses the same High-Low Propulsion System as the M203.
In 2004, the Army announced a requirement for a commercial off-the-shelf 40 mm grenade launcher. It had to be more reliable, ergonomic, accurate, and safer than the M203. It had to be able to fire all 40 mm low-velocity grenades but be loaded from the breech to accept future longer projectiles. Heckler & Koch's submission was selected in May 2005.
After the U.S. Army at Picatinny Arsenal conducted a competitive bidding process for a new 40 mm grenade launching system, Heckler & Koch was awarded a contract to provide the XM320 beginning in 2006. The M320 was developed from but is not identical to the Heckler & Koch AG36 (a key distinguishing feature being the addition of a folding foregrip ahead of the trigger for use when the weapon is in stand-alone configuration, a feature the AG36 lacks). The M320 entered production in November 2008.
Fielding of the M320 was planned to begin in February 2009, with 71,600 GLMs planned to phase out the M203 by 2015. The weapon was officially fielded in July 2009 at Fort Bragg by the 1st Brigade Combat Team, 82nd Airborne Division. In June 2017, Bravo Company, 2nd Combat Engineer Battalion became the first U.S. Marine Corps unit to be issued the M320. Following initial experiments, the Marines expect to issue 7,000 launchers between 2019 and 2022.
The M320 has three major parts: a grenade launcher with rifled barrel, Day/Night Sight (DNS) produced by Insight Technology, Inc and a hand held Laser Range Finder (LRF). Some of the benefits are: