The 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.

Product Manager Individual Weapons (US 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. The M320 entered production in November 2008. The unit was officially fielded in July 2009 at Fort Bragg by the 1st Brigade Combat Team, 82nd Airborne Division.

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