The 40 mm Mk 19 machine gun was originally developed by the US Naval Ordnance Station, Louisville, Kentucky, in order to provide the US Navy with a suitable weapon for riverine patrol work in Vietnam.

It was designed around the high-velocity 40 mm M384 grenade round. Work commenced in July 1966 with the first functioning models being completed early the following year.

The Mk 19 Mod 0 was effectively used in combat in Vietnam. A product improvement programme, initiated bytheUSNavyin 1970-71, resulted in the Mk 19 Mod 1 version and some 600 of the original Mod 0 version being converted to this improved specification.

In 1974, the Naval Ordnance Station resumed production, making 605 Mod 1 weapons for Israel and these were subsequently used by the Israeli forces on ground, vehicle and boat mountings.

In 1976, Louisville began a further improvement programme aimed at improving reliability and safety, reducing cost and simplifying maintenance. The resulting Mod 3 has 47 fewer parts and can be stripped without the need for special tools.

A contract for production of the Mk 19 Mod 3 weapon and the Mk 64 Mod 4 mount was awarded by the US government to Saco Defense Incorporated in October 1983. This and subsequent contracts have seen deliveries of the 40 mm Mk 19 Mod 3 weapon and mounts to the US Army, Air Force, Marine Corps and Navy throughout the mid-1990s.

By 1999, total production of the weapon had reached 23,000 units with production still under way for home and export markets.

The Mk 19 is an air-cooled, blowback type automatic machine gun that fires a variety of 40 mm grenades at a muzzle velocity of 241 m/s. These include the M430 high-explosive dual-purpose anti-personnel and armour-piercing round and the M918 flash bang practice round. A variety of non-US 40 mm grenades can be fired including the Diehl HEPFF-1 anti-personnel round with tracer and Nico's tracer marker round which has recently been type classified by German MoD. Specialised less lethal ammunition, for example CS and pepper is also available from NICO. With a maximum effective range exceeding 1,500 m, it can be used to engage personnel and light armoured vehicles. The system can be ground, vehicle or turret-mounted.

Ammunition is belted by a unique link that stays with the cartridge case and is ejected with the case after firing. The gun is fired from the open bolt position with the ammunition feed occurring during recoil, similar to the M2 12.7 mm machine gun.

It can be fired manually or remotely by use of an electrical solenoid, a single round at a time or fully automatically at 300-400 rds/min.

The Mk 19 comprises five major subassemblies: the bolt and backplate; seat; top cover; feed slide and tray; and receiver. It is fitted with a sight, spade grips and charger assembly similar to those on the 12.7 mm M2 machine gun.

The Mk 19 can be mounted on virtually any vehicle, boat or helicopter using the Mk 64 Carriage and Cradle. It can also be mounted in a turret, such as the US Marine Corps 40/50 turret. Examples of vehicles on which the Mk 19 is mounted are the HMMWV, Chenowth Fast Attack Vehicle, M113 APC, Land Rover and US Marine Corps AAV7A1 amphibious vehicle.

Current production models are also available with various fire-control mountings and brackets to mount any type of fire-control system such as the Ring Sight WC-30, which is sighted out to 2,000 m.

Status

In production. Adopted by at least 27 countries including, Ecuador, Honduras, Israel, Mexico, Sweden, UK and the USA and other undisclosed countries. As far as it is known, the US Marine Corps is the only user of this weapon in a turret-mounted role. This turret was originally developed and built by the then Cadillac Gage (now Textron Marine & Land Systems) as the 40 mm/12.7 mm Upgunned Weapons Station. More recently AV Technology have developed a turret armed with the same weapons called the one-man Multi-Gun Turret System (MGTS). Details of both of these turrets are given in the AFV turrets and cupolas section. It is also installed in the Kollmorgen Compact Lightweight Armored Weapon Station covered in the AFV turrets and cupolas section.