M90 shotgun

The M90 Close Assault Weapon System (CAWS), also known as the M90 Close Assault Shotgun, M90 assault shotgun, or simply the M90, is a pump-action shotgun in service with UNSC. It is a military variant of the prolific DTM series of shotguns from Weapon Systems Technologies.

Design
The M90 is a pump-action shotgun, chambered in the extremely powerful 8-gauge magnum shell, and feeding from a 12-round, dual-tubular, non-detachable magazine. It is designed as a more practical and cost-effective recreation of Misriah Armory’s M45E Tactical Shotgun, though in UNSC service it is considered to be functionally identical. The magazine of the weapon is prominently positioned above the barrel, with the weapon’s glowing iron sights mounted atop it and the receiver located just behind, facing upwards, roughly in-line with the trigger. A flashlight is integrated into the weapon’s forend, which also features a prominent reddish button.

Functionality
As is typical of human firearms, in order to discharge the weapon, the trigger positioned at the top of the pistol grip must be depressed. If the weapon is loaded with standard 8-gauge magnum ammunition, the weapon's firing will take the form of a spray of pellets, referred to as "buckshot", which are quite powerful at close range but lose damage efficiency as the spray disperses and loses energy. Once the chambered round is fired, to do so again, the forend of the weapon (which serves as the weapon's foregrip) is slid back across the weapon’s underside in the directing of the stock, retracting the bolt and removing the spent shell from the firing chamber. When the forend is fully retracted, the spent shell will have been ejected, and the way will have been cleared for the elevator to position a new round for the bolt to carry into the chamber when the slide is once again pushed forward in the direction of the muzzle. Once the weapon’s magazine is expended, new rounds must be inserted one at a time into the receiver to continue firing. It is possible at any time to top up the magazine with additional ammunition until it is full.

Depictions
There are two primary depictions of the M90 CAWS. The first depiction is the original seen in Halo: Combat Evolved. The more recent depiction, however, is that seen in Halo 2, Halo 2: Anniversary campaign and Halo 2: Anniversary multiplayer. In the Halo: Combat Evolved depiction, the weapon features a smooth magazine with a chrome finish, and the iron sights glow blue. In Halo 2 and Halo 2: Anniversary, the magazine of the weapon has a dull grey finish with ribbed indents, and the iron sights glow green. In Halo 2: Anniversary multiplayer, the magazine retains its ribbed design but with a glossy black finish. In Halo: Combat Evolved, but not successive depictions, when the weapon is reloaded after being completely emptied, the weapon’s action is worked to chamber the first round.

Performance
The M90 is a devastating weapon in close, confined environments, with a loud report and strong recoil. The spray of pellets from the weapon mean that at slightly longer ranges, it can be used to hit clusters of targets simultaneously, but also makes the weapon inefficient at extended ranges due to the low ratio of shot which hits the target to the amount of shot fired. The M90's powerful cartridge makes it capable of efficiently engaging and defeating enemies with energy shielding within effective range. The Covenant learned to be wary of this weapon in the urban environments typical of engagements throughout the Covenant War, noting its close-range power.

History
The M90 was a common close-range battle implement in the service of the UNSC throughout the Covenant War. It saw service in the hands of John-117 during Operation: SILENT STORM, but its most prominent usage came in 2552. It played a notable part in the Battle of Installation 04, being used by UNSC marines against the Covenant and Flood. An M90 was also present during the ensuing Skirmish over Threshold. It went on to be widely utilized during the Battle of Earth. In particular, the Master Gunnery Sergeant who oversaw John-117's issuing with his new MJOLNIR Mark VI armor was killed on Cairo Station while using an M90 to defend his armory from elites. They were brought on the UNSC In Amber Clad, and thus were employed throughout the Battle of Installation 05.

Trivia

 * In Halo: Combat Evolved, the M90 shotgun shares its reticule with the then-PC-exclusive flamethrower.
 * In the second issue of Halo: Fall of Reach - Boot Camp, the captain of the retrieves several shotguns from a cryo chamber. In the first two panels, the shotguns appear to be M45s, though they resemble M90s in subsequent panels.
 * In Halo 2: Anniversary, if the player uses Active Camouflage while the M90 is equipped, the shells will be the only objects still visible. This could be because the shells are technically not attached to the shotgun (like the magazines in other weapons) but rather held inside the weapon until ignited and fired. This is best seen when playing as the Arbiter.
 * In Halo: Combat Evolved, the shotgun is the most effective weapon in the game against most Flood forms. A single shot is capable of killing Flood combat forms and Flood carrier forms and works best when paired with a weapon with a high-rate of fire such as an MA5B assault rifle to deal with Flood infection forms. The shotgun is still effective in later games, but not to such a degree as, starting in Halo 2, infection forms can revive deceased combat forms unless the body is destroyed. Halo: Combat Evolved lacked this resuscitation ability for the Flood.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Halo: First Strike
 * Halo 2
 * Halo Graphic Novel
 * Breaking Quarantine
 * Halo Wars
 * Sadie's Story
 * Halo Legends
 * Homecoming
 * Origins
 * The Package
 * Halo: Blood Line
 * Halo: Fall of Reach
 * Boot Camp
 * Halo 2: Anniversary
 * Know Your Enemy
 * Halo Mythos
 * Halo Wars 2
 * Halo: Fireteam Raven
 * Halo: Silent Storm