Sometimes, 5.56mm just isn’t going to get the job done – and neither will any other standard rifle caliber. Shoulder fired rockets are heavy, which limits carrying capacity, and can’t fill all needs with their warheads. That’s why most militaries use reloadable 40mm grenade launchers as key supplemental firepower for their infantry squads, while leveraging the round’s array of special-purpose ammunition types.
HK’s M320 seems set to become the US Army’s new under-weapon/ hand-held 40mm grenade launcher. The M320A1 fits on the Army’s M4 or HK’s HK416, while the M320 fits M16 rifles. They appear to be the M203’s successor in the US Army and associated Reserve or Guard units, and like their predecessor, M320s attach or detach from a rifle with no special tools required. Unlike their slightly lighter predecessors, the double-action M320s include a side-loading breach for longer 40mm grenade types, instead of the M203’s slide-forward-to-load operation. An optional day/night sight, and a handheld laser rangefinder for the grenadier, make the system more accurate, as do mechanical sights that maintain their zero via direct mounting on the launcher, instead of the rifle. If required, a detachable sliding buttstock quickly converts the M320 from an under-weapon addition to a single-purpose “bloop tube.”