Mk 19

The Mk 19 is a mounted grenade launcher that appears in Call of Duty 4: Modern Warfare.

Call of Duty 4: Modern Warfare
In Call of Duty 4: Modern Warfare the Mk 19 is a helicopter-mounted, medium fire rate grenade launcher available in the level "Shock and Awe". It cannot be moved by the player but is mobile as the helicopter it is mounted on moves. The Mk 19 is prone to overheating and this is visible on the HUD through a bar that fills with red color when the weapon is fired. It is an explosive weapon and can take out tanks, troops and anti-aircraft emplacements easily.

Trivia

 * Coincidentally, the Mk 19 can fire 19 grenades in a row (holding the trigger down) before overheating.
 * Mk 19 uses a longer 40mm grenade than the M203, and also fires the grenade round at higher velocity than M203 grenade round, so Mk 19 ammunition cannot be used in the M203 grenade launcher despite having the same diameter.
 * BMPs take 2 shots before they explode.
 * The player can blow up oil tankers with the Mk 19, which tends to obscure the player's vision. It is also possible that the tanks will take 1 shot to make it explode. You have to aim carefully though.
 * Grenades fired will travel completely straight and never arch.
 * Friendly vehicles cannot be destroyed by the Mk 19, however you will still recieve the friendly fire penalty.
 * The player can't see their hands when using the Mk 19.
 * This weapon only appears in the mission "Shock and Awe", in Call of Duty 4.
 * Sgt. Paul Jackson is the only one ever seen using the Mk 19, even though he isn't technically "seen".