XM320 GLM / SAM GLM (Grenade Launcher Module / Stand Alone Module)

Related to the AG-C/EGLM and AG36, the HK XM320 GLM is a 40 mm single-shot add-on grenade launcher selected to replace the U.S Army’s current issue M203.

The XM320 can fire all of the "low velocity" high explosive (HE), high explosive dual purpose (HEDP), irritant gas, smoke, and illuminating rounds previously fired from the M203. However, because its breech opens to the side, instead of the pump-style of the M203, the XM320 can also fire a variety of newer rounds that are longer, specifically certain non-lethal rounds. It is expected that the U.S. military intends on changing the  XM320 to M320, removing the "X" (experimental) designation when the launcher is type classified (TC) and will receive a U.S. Government national stock number (NSN).

The XM320 program takes full advantage of existing Commercial Off-the-Shelf (COTS) technology. The XM320 was envisioned, tested, and selected with operator involvement in a full and open competition in 2005 — without the need to invest U.S. government R&D funds or employ a lengthy and costly development process.

Like the HK AG-C/EGLM, the mechanical ladder sights on the XM320 are located on the side of the grenade launcher, not the host weapon, so they do not require re-zeroing every time the launcher is reattached to the rifle or carbine. An optional Day/Night Sight (DNS) provided by Insight Technology, Inc., with ballistic computer, infrared illuminator and infrared laser may be mounted to the XM320 for both day and night fire capability. This system provides first round hit probability in 5 meter increments "out to a maximum effective range of 300 meters" and the DNS can be tandem mounted with the mechanical sights. 

The XM320 has a double action trigger, ensuring true primer strike, with an ambidextrous safety and ambidextrous barrel release lever. In case of misfire, the XM320 user merely has to pull the trigger again, versus the M203 operator who has to cycle the breech to re-cock the firing pin, then pull the trigger again.

The XM320’s side-loading, rifled barrel is constructed of aluminum for lightweight and is spring actuated for quick loading and unloading. The XM320 barrel measures 8.46 inches (215 mm), shorter that the 11 inch (279 mm) barrels found on the AG-C/EGLM and AG36.

With the addition of a retractable buttstock, the XM320 can be used as a stand-alone launcher. An integral MIL-STD (Picatinny) rail also allows a folding vertical foregrip to be added. In this configuration, XM320 can be used effectively as a “grenade pistol” in confined spaces without the buttstock attached.

Like the M203, the XM320 attaches to the M16 rifle and M4 carbine, and can also be mounted on the HK416, HK417, and a variety of other weapons.