The explosive art of fire support: MK19 and M203

The evolution of grenade launchers has reached new heights with the development of the M203 and MK19. The M203, a single-shot 40mm under-barrel launcher, and the MK19, a fully automatic 40mm grenade machine gun, have revolutionized infantry capabilities.

M203 uses a high-low propulsion system to fire a 40-mm round.

The firing pin strikes the primer, whose flash ignites the propellant in the brass powder-charge cup

inside the high-pressure chamber.

The burning propellant produces 35,000 psi chamber pressure, which ruptures the brass powder charge cup at the vent holes and allows the gases to escape to the low-pressure chamber in the cartridge case.

There, the pressure drops to 3,000 psi and propels the grenade from the muzzle at a velocity of 250 fps.

The grenade’s 37,000-rpm right-hand spin stabilizes it during flight and applies enough rotational force

to arm the fuze.

The weapon is unloaded with the barrel open and fired from a closed bolt.

It must be cocked before it can be placed on SAFE.

Originally, the MK19 grenade launcher was made to replace the earlier hand-cranked multiple grenade launcher, the MK18.

The design of the MK18 was relatively lightweight, though firing with a hand-powered crank rather than a butterfly-style trigger reduced the accuracy of the weapon.

Development of the MK19 automatic grenade launcher began in July 1966, and by October 1967, the first three working prototypes of the new weapon were ready for official field trials. 

The production MK19 Model 0 grenade launchers entered service in Vietnam in early 1968, onboard riverine craft like PBR and UH-1 Huey gunship helicopters belonging to the US Navy.

Around 1971, the basic design was slightly improved, and the type was classified as ‘Mark 19 Model 1’.

The Navy made further improvements to the weapon, resulting in Mod 3 in 1976. Mod 3 was adopted by the U.S. Army in 1983 and remains in service to the present day. 

Mounted on a tripod or on the platform of multiple vehicles, it is the main suppressive weapon for combat support and other service support units. 

The MK19 Grenade Launcher is capable of defending against hovering rotary-wing aircraft.