The United States Army has selected the single-shot 40mm HK M320 GLM ("Grenade Launcher Module") as its replacement for the venerable single-shot 40mm M203 - an under-slung grenade launcher in service since 1969. The M203 saw extensive service in the Vietnam War and beyond but held several limitations in its design - most prominently with its sights and single-action fire mode. The M320 is a development of the Heckler & Koch Defense (primarily of Germany though also based in the US), better known for their submachine guns, assault rifles and precision systems and is based on their AG36 series (visual similarities are quite obvious between the two). Heckler & Koch secured the US defense contract in 2006 after a good showing at the famed Picatinny Arsenal. Production of M320s then began in 2008 while quantitative orders were placed by the US Army in 2010 for 6,000 units at a cost to American tax payers of $13.7 million. During competition to fulfill the US Army contract, the M320 was known under the designation of "XM320". An M320A1 designation also exists.
The M320 is a handy, compact system capable of firing various grenade rounds as missions require. The basic design sports a stout frame with integrated shoulder, pistol grip and fold down foregrip. The weapon maintains only one mode of fire beyond the safety feature, this managed by a simple HK-style selector switch found along both sides of the receiver rear. The double-action trigger is solid and embedded ahead of the pistol grip and protected over in a thick ring guard. There is a flip-up sighting device affixed to the upper left side of the receiver, keeping it clear of primary rifle functions and sighting when set under the barrel a primary weapon (an issue found with the M203). The barrel is set within the receiver with its breech opening to the left hand side for reloading. It is tubular in its external design and rifled in its internal design. The M320 can be used as both a stand-alone weapon (as in the Vietnam-era M40 launcher) or as an under-slung, secondary weapon and can accompany a carbine/assault rifle system like the M4 or M16 (as in the M203). When paired with another weapon, the adjustable stock of the M320 can be removed. The system weighs in at just 3.3lbs and sports an overall length of 13.7 inches making it highly portable in any battlefield role. While the M320 is single-shot in its design, a trained grenadier can fire between 5 and 7 rounds per minute, making repeating fire possible for tactical situations. There is some noticeable recoil to contend with when firing the M320 though there is only a light smoke discharge so as not to give away the position of the firer, each projectile following an arced flightpath.
The M320 is cleared to fire several types of US Army and NATO-standard munitions including high-explosive (HE), smoke, illumination, training and "less than lethal" rounds - the latter for riot/crowd control. Acceptable rounds are "40x46mm SR" in caliber. High-explosive grenades can be used to dislodge or kill enemy elements under cover whilst smoke grenades can be used to "blind" the enemy to friendly movements. Illumination rounds can light up a darkened sky for a time, allowing easier recognition of friend and foe in night environments. Maximum range of the M320 system is listed at 400 meters while an effective range of 150 meters is given.
Current (2019) users of the M320 series include Canada, Germany, Hungary, Malaysia, Netherlands, Norway, Philippines, the United Kingdom, and the United States (Army and USMC services).