M319 grenade launcher

The M319 Individual Grenade Launcher, more formally known as the Individual Grenade Launcher, Caliber 40mm, M319, is a single-shot, break-action explosives launcher used by the United Nations Space Command, specifically the UNSC Army. Due to its simplicity, ruggedness, and firepower, it has been a mainstay weapon in the UNSC Army since its adoption in 2263, and has seen action in several armed conflicts during nearly three centuries of use, with the Human-Covenant War as the most prominent. It saw use during the Fall of Reach.

Design details
The grenade launcher has two firing modes. The first launches a single grenade at around normal grenade speed: after hitting a surface, the grenade detonates on impact with an opponent or after the time of a frag grenade's detonation, in which case the grenade will explode after bouncing off the ground once. The second firing mode shoots a grenade that explodes when the player wishes. This is performed by holding down the trigger, which fires the grenade but merely primes it; it will only explode after the trigger is released. This enables the player to lay a trap and essentially creates an explosive with a dead-man's trigger (a trigger that will go off once it is released, e.g. when the player dies). Like the fragmentation grenade in Halo: Reach, a player will take damage if hit by the grenade when it is merely primed.

Also, the grenade emits a form of EMP, similar to that of the plasma pistol, that can temporarily disable vehicles and energy shields, but only when used in the manual detonation mode.

The weapon utilizes a break-action breech-loading system: after firing one round, the weapon must be reloaded, like many twentieth century shotguns.

Trivia

 * The Grenade Launcher has multiple nicknames among the fan community and Bungie alike, including "pro-pipe", a reference to the numerous grenade launchers in first-person shooter games, which have been collectively dubbed "noob-tubes".
 * The M319 IGL, having been manufactured in 2263, is the oldest known active service weapon utilized by the UNSC.
 * In the Beta, if a player fired the M319 and held the trigger until he/she died and someone else picked up the weapon, the player holding the M319 would take control of the dormant grenade.
 * The M319 bears a very close resemblance to the real-life Russian GM-94. However, their similarities are merely aesthetic, as the GM-94 is a magazine-fed pump-action grenade-launcher using 43mm grenades. The M139 also bears a close resemblance to the American Springfield Armory M79 grenade launcher in both aesthetic and functional fronts. The two are break-action launchers that fire 40mm shells.
 * When reloaded, the M319 does not extract any empty shell casing. This could mean that it uses either a caseless grenade round or a self-propelled grenade.
 * In the alpha build, the M319 has a red light on its side. This was removed later in the beta build.
 * The counter on the left of the weapon switches from "ARMED" to "IN AIR" after the round is launched, and to "BOOM!" upon detonation.

List of appearances

 * Halo: Reach