Grenade Launcher

Overview

Simply put, a grenade launcher is a gun-like weapon that fires grenades instead of bullets. Grenade launchers provide the inherent benefits of using of a gun (enhanced accuracy, higher shot velocity and distance), greatly improving upon the traditional practise of throwing grenades by hand. Much like conventional firearms, grenade launchers are able to fire a variety of ammunition. For example, tear gas ammunition is often used by riot police as a non-lethal means of subduing dangerous rioters. Alternatively, the launcher can also be used by the military in lethal ways through the use of  high explosive grenades.

Grenade launchers exist as both stand-alone weapons and firearm extensions, which may be mounted onto the body of a gun such as the M4A1. Heavier and more durable models can be mounted on tripods or vehicles for improved stability and launching power.  These heavier models will usually use a belt fed ammo system, reducing reload times and improving shot frequency.

Launcher Types

There are a few common types of grenade launchers that can be found in many games.  We'll classify the launchers into two types by weight, size, and durability as Light/Medium and Heavy launchers. 
   

Light / Medium launchers
There are three main types of Light or Medium Grenade Launchers: Stand Alone, Mounted, and Muzzle-fired .

Types of Light / Medium grenade launchers
The Stand Alone Launcher is a complete weapon in itself. This weapon exists as the simplest approach to launching grenades (that put enemies in a world of pain). In games, the grenades shot by Stand Alone Launchers often have timed or impact fuses. Sometimes, the altfire button is designated to an alternative fuse-type not assigned to the primary fire key. For example, if the primary fire uses an impact fuse (in which the grenade explodes upon contact with a target), the alt fire will use a timed fuse (in which the grenade explodes after a set time period). An alternative control scheme often employed is to use one fire key for both fuse types. In this scheme, when the fire key is tapped, we launch an impact grenade, whilst holding the key will launch a timed fuse.
The Mounted Launcher is a bit more complicated than the Stand Alone.  Unsurprisingly, the Mounted Launcher is a mounted attachment on the barrel of an assault riffle, such as an M4A1 or an M16.  For this launcher , most games grenade firing is assigned to an alt fire key as rifle firing is designated to the primary firing key. However, other games often use a single firing button, but require an ammo switch to be made before grenades can be fired. Lastly, in rare instances, some games classify this as its own weapon. Launchers are usually mounted on the bottom rail of the gun's barrel, instead of side or top rails.
The Muzzle-Fired is a very specific type of launcher. This launcher is an attachment designed for the end of a gun barrel, typically a rifle. Specifically, the force produced by the rifle firing a blank cartridge/bullet is used to fire specialized ammo, called Rifle Grenades from this attachment. Aside from rifles, Muzzle-Fired attachments can be used with shotguns and assault rifles. Often in games, the blank cartridge and bullet used to propel the grenade aren't simulated.

 

Feeding Systems

When the launcher is used alone or as a mounted attachment on a gun, they come often in single-shot or multishot models that can hold anywhere from 4 to12 rounds in games featuring reloading with this weapon Reloading is accomplished using a breach action for the single-shot models, pump action for models with a tube magazine (rarely found in video games), or semi-automatic for the models that  use a magazine or a drum (the most common in video games) Another rare type of launcher reloading involves barrel feeding, which allows it to load grenades into the same tube.                - The 3 GL from Metal Storm is a good example of this system. A few models can fire airburst grenades, such as the OICW featured in SOF II

 

Heavy grenade launcher
The Heavy grenade launcher is generally mounted either on a vehicle or a tri-pod. They are capable of automatic firing using a belt fed system. Like many mounted weapons in games, the Heavy grenade launcher typically has infinite ammo.

Outside of the general launcher types mentioned above exist few, but unique variants. The most idiosyncratic of all of these is the grenade-launching pistol. Specific models of this weapon include the HK 96 and the M203.
 
Grenades, as drops in games, will come in shell boxes, magazines or drums, or in single shells when they are placed through the game's levels.
 

Using Multiple Ammo Types

There are several kinds of ammunition for grenade launchers in video games. Not all grenade launcher ammunitions available in real life exist in games, but (hopefully) may appear in future games. No matter what ammo a launcher uses, it's power will always vary depending on its fuse system and payload.

Fuse System 

• Timed (grenades using this system will often bounce if colliding with a target before the timer has counted down)
  

1. Airburst (Programmable)
   
2. Explode when they come in contact with a damageable target (there are a lot of games using timed grenades with this kind of fuse, such as Quake or the Unreal Tournament games) 
3. Sticky (will stick on enemies and detonate after a few seconds)

• Remote Controlled, also exist in sticky variants. These grenades require an addition button press from the user to initiate detonation.
  

• Impact (explode upon contact)

• Proximity (explode upon target's entry into trigger-area surrounding grenade)