The M320 program takes full advantage of existing Commercial Off-the-Shelf (COTS) technology and rapid acquisition procurement. The M320 was envisioned, tested, and selected with operator involvement in a full and open competition in 2005â€”without the need to invest U.S. government R&D funds or employ a lengthy and costly development process.
The U.S. Army â€śtype-classifiedâ€ť the M320/M320 grenade launcher system with National Stock Numbers (NSN) and it is now in the current Army logistics support network. First units were fielded in the summer of 2009 for operational deployment with U.S. forces in Southwest Asia.
Like the related HK AG-C/EGLM, the mechanical ladder sights on the M320 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) provides first round hit probability in 5 meter increments out to 400 meters and the DNS can be tandem mounted with the mechanical sights.
The M320 operates in double action mode, with an ambidextrous safety and ambidextrous barrel release lever. In case of misfire, the M320 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 M320â€™s side-loading, rifled barrel is constructed of aluminum for lightweight and is spring actuated for quick loading and unloading. The M320 barrel measures 8.46 inches (215 mm), shorter that the 11 inch (279 mm) barrels found on the AG-C/EGLM and AG36, but considered the optimum for saving weight and projectile velocity.
With the addition on a retractable buttstock, the M320 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, M320 can be used effectively as a â€śgrenade pistolâ€ť in confined spaces without the buttstock attached.
Like the M203, the M320 attaches to the M16 rifle and M4 carbine, and can also be mounted on the HK416, HK417, and a variety of other weapons equipped with under-swung Picatinny rail systems.