The Mk 19 grenade launcher is an American grenade launcher that was designed in 1966 and entered service in 1968 with the US military during the Vietnam War and continues to see service even today. The Mk 19 grenade launcher is fully automatic, and is capable of firing a wide variety of ammunition types.
The Mk 19 was originally designed in 1966 by Naval Ordnance Station Louisville, or NOSL. NOSL originally designed the Mod 0 version of the Mk 19 during the Vietnam War, but was deemed unreliable and unsafe for use. The Mod 1 was later developed, and six of them were successfully tested on US patrol craft. Further refinements to the design paved the way for the introduction of the Mod 3 in 1976, which was adopted in 1983 and is still being used by the US Army till this day. When originally introduced, the Mk 19 replaced the older Mk 18 grenade launcher.
The Mk 19 is an air-cooled, belt-fed fully-automatic grenade launcher usually manned by a crew of two. It operates on the blowback principle, specifically, the Advanced Primer Ignition blowback principle, or API blowback for short, which is where the primer of the grenade is ignited while the bolt is still moving forward and before the grenade is fully chambered. The weapon has a fairly low rate of fire of about 375 rounds per minute, which allows the weapon to cool off sufficiently before firing the next round, preventing cook-offs. In addition to that, the Mk 19 also fires from an open bolt, which helps to prevent cooking off even further. The weapon has a flash suppressor which only serves to protect the firer's eyes and not as a way conceal the weapon. When used, it is usually seen on either a tripod or on a vehicle mount; the latter is the preferred method as the Mk 19 as very heavy, weighing in at a whopping 77.6 pounds (35.2 kilograms) without accessories; however, it has rather low recoil, so the weapon has been adapted to be used on various vehicle platforms such as the Humvee and IAV Stryker. The Mk 19 has dual charging handles mounted on pivots, which when pulled, feeds the first round onto the bolt face. Recoil from the weapon when fired blows the bolt back and feeds a new round onto the bolt face and pushes the spent cartridge off it. Grenades are fed from the left.
The Mk 19 uses a variant of the 40×53mm grenade as standard ammunition, the high-explosive dual-purpose M430 grenade, which has the ability to kill anybody in a five-meter radius. Despite being of a similar caliber, Mk 19 grenades are incompatible with the M203's 40×46mm grenades, as M203 grenades develop lower chamber pressures when compared to those used in the Mk 19. Airburst grenades jointly manufactured by General Dynamics and Advanced Material Engineering Pte Ltd, a subsidiary of Singapore-based company ST Kinetics, are compatible with the Mk 19. The jointly-manufactured airburst grenades have timed fuzes that are completely programmable which computes and programs the detonation time into the fuze. When fired, a timer in the fuze counts down, and once it reaches zero, the grenade detonates.