M90 shotgun

"I believe that the sound of racking the pump of a shotgun is universally recognized as ‘kiss your ass goodbye’."

- Unknown Marine

The M90 Close Assault Weapon System (abbreviated M90 CAWS), is the United Nations Space Command's primary shotgun and is one of the most lethal infantry weapons used by front line forces.

Design Details
The M90 Shotgun is a pump-action, magazine-fed, dual tubular non-detachable type weapon. The Weapon System Technologies DTM series shotgun is the most common shotgun employed by UNSC Special Forces, law enforcement agencies, and sportsmen. The M90 has been in service for over 27 years and its design has changed very little. The M90’s immense power, ease of use, and reduced capacity for puncturing the hulls of spacecraft over many other UNSC weapon systems with standard 0000 ammunition are greatly appreciated. The M90 is often employed in urban conditions where the tight spaces are conducive to the shotgun's wide spray for defensive purposes and CQB combat. The military issued DTM series comes standard with an adjustable stock and pistol grip, although there are different models like the WST DTM/LE model which has a solid stock and no pistol grip. The DTM series of shotguns are available in 20-Gauge and 10-Gauge for the civilian market; the 8-gauge is only sold to law enforcement and military agencies.

Ammunition
The M90 Shotgun uses the Soellkraft 8 Gauge Magnum Shotgun Shell. This is an incredibly large round, not used by any modern military. Recoil has been said to be relatively low. It is assumed that shotgun technology must have advanced enough to suppress the recoil.

Advantages
The M90 Shotgun fires 15 spreading pellets per shot. The combined force of each relatively weak pellet does a significant amount of damage against almost any type of infantry, and the shells wide spread in certain situations can inflict shrapnel damage to multiple infantry. The M90 Shotgun's powerful 8 gauge shell can punch through armor and Energy Shields easily, making the M90 a great weapon for taking on heavily armored infantry, and lightly armored vehicles. The M90's top loading system allows a user to reload the shotgun with speed and ease for quick firing.

Disadvantages
While highly effective at close range, the M90 is rendered useless at long range, and must be used in conjunction with a medium or long range weapon. The shotgun's pattern is extremely loose, and fans out quickly, thus at farther ranges, only one or two pellets out of the 15 might hit. The M90, being a pump action shotgun, must be cocked after every shot before it can be fired again; the M90 must also be reloaded shell by shell and does not use any type of external magazine. This can make reloading time-consuming when in combat situations, but it is useful to be able to interrupt the reloading and shoot after you load a shell. In open close-quarter situations, the wide spread of the shell can potentially harm friendly infantry if the shotgun is fired at both the enemy and friendly troops.

Influence
The mechanical design of the M90 shotgun is loosely based on the South African Neostead shotgun which features dual six-round top-loaded magazines. The weapon features two integral tube magazines with a total capacity of thirteen rounds (6+6+1) and ambidextrous bottom ejecting shells. It is chambered for standard 12-Gauge 2.75-inch cartridges. The aesthetic design is a composite of multiple pump-action designs, most notably, the Mossberg 500.

Campaign

 * One of the most dominating weapons in the Halo Trilogy, the Shotgun shows its most effective side in The Library in Halo: Combat Evolved and in Sacred Icon in Halo 2.
 * This weapon is easily the best choice in the game for taking out powerful enemies such as groups of Flood Combat Forms, Elites, and Brutes. Even on Halo: Combat Evolved Heroic difficulty, it is possible to take out shielded Elites with as few as two shells, and only on Legendary do the Flood become capable of surviving a direct hit from the shotgun.
 * In Halo 2, Brutes, Councilors and Ultra Elites are the only ones that can survive a point blank shotgun blast on Normal difficulty. Hunters can be killed by shooting directly into the exposed orange Lekgolo. However, on Legendary difficulty, any rank higher than a Minor Elite's shielding and health can withstand a point blank shotgun blast. Beware, for the Flood can wield shotguns to devastating effect, since they have an extremely long jumping range. In Halo 2 Brutes also wield shotguns.
 * Despite its huge firepower, it will take around 2-3 shots to kill a Brute Minor or Brute Captain.
 * In Halo 2, shotguns are largely ineffective against Brutes on any difficulty.

Multiplayer

 * The shotgun's effectiveness in multiplayer games varies depending on the terrain; indoors and in tight spaces, the shotgun is unbeatable, and some consider it superior to the Energy Sword, possibly because there is a slight delay between pressing the trigger and the slash of the sword, while the Shotgun is instantaneous. Most players can utilize this fact to earn a Bulltrue medal relatively easily, though caution should be exercised, as the timing is very difficult to master.
 * You have about one shot to kill your opponent after you ambush them. If you shoot and don't succeed to kill them, your opponent has a chance of recovering and killing you, most likely taking your prized weapon away from you.
 * Many players carry the shotgun and a weapon that is very effective at medium and above ranges such as the Sniper Rifle, Beam Rifle, Covenant Carbine, M6D Pistol, or BR55 Battle Rifle, thus making for a more flexible arsenal.
 * Continuous firing by using the magazine and loading one shell then firing does not affect the rate of fire significantly, prompting a few players to employ a tactic dubbed "shotgun sniping" as suppressive fire across medium-sized maps.
 * The Shotgun can finish enemies off safely and quickly by shooting them at a decently close range, then striking them with a melee attack immediately afterward, guaranteeing an instant kill.
 * When you have a shotgun, it is advisable to watch your team's sniper. That way you can defeat anybody that attempts to flank the sniper. It is easy to do this on The Pit.
 * It is best to carry a Battle Rifle with you, or some other medium to long range weapon. If not, have a teammate with you who will have one. On the maps Snowbound and Epitaph, many people prefer to wait by shield doors, preparing to ambush and instantly kill those who come through. If you're charging at at enemy while firing your Assault Rifle hoping to finish him off with a melee attack, and the enemy is charging at you but not firing, chances are he has a shotgun and plans to surprise you with it when you get within killing range.

M90 Models
Not much has changed in the shotgun's design since its conception. The weapon's power lies in the great stopping power of its quad-ought (or 0000) ammunition load, which, is extremely powerful in close-quarters combat.

M90 Mk I
Introduced in Halo: Combat Evolved and is arguably the strongest version. The M90 Mk I can hold 12 shells, and the player can carry up to 60 more shells for a total of 72 shells. It has the longest and most realistic effective range of all the three models, and its fifteen tungsten pellets could kill, weaken or injure targets at short to medium ranges. Although it is more likely to kill a closer ranged enemy as the shotgun is weak on further distanced enemies, the shotgun could also kill nearly any infantry target at point blank range. It even has the capabilities to take on lightly armored vehicles, such as the Ghost effectively. Players could hold the trigger button down for continuous fire. To melee, the player swings the Shotgun up and brings the butt of the weapon on someone's head/front. If the player fires the entire magazine or if the player picks up a Shotgun without a full magazine and fires it empty, the character model will rack the shotguns pump after reloading, although most players usually opted to reload after every shot. This version of the M90 shotgun had a quicker reload than the Mk. II model.

M90 Mk II
The second model, the M90 Mk II, used in Halo 2 changed significantly from the Mk I. The only difference in appearance, with this model is the green Iron Sights instead of blue and the stock's shape. The melee is much faster than the Mk I's, swinging the Shotgun horizontally instead. Its performance is also drastically different as it can not kill targets at more than a few feet away, though a quick shoot-melee combo would usually kill an enemy very quickly. The player can only carry 36 spare shells for a total of 48 shells. Unlike the previous version, it has almost no stopping power when used against vehicles, and like before, with the range decrease, its effectiveness against the Flood was reduced slightly. It probably took this change as Bungie introduced the Energy Sword as a usable weapon, and wanted to "even the odds". The weapon's action does not cycle after reloading, unlike the previous iteration of the M90.

M90A
The third model, the M90A, is used in Halo 3 and Halo 3: ODST. There are a variety of graphical and gameplay changes from the previous models. The blue iron-sights have been reintroduced, it has a longer barrel and the flashlight is now mounted on the side. Unlike the older models which had a 12 shell magazine, the M90A only has a 6 shell magazine. The player can carry 30 spare shells for a total of 36 shells. To make up for this, its effective range is far greater than the M90 Mk II, as it can kill targets at two or even three times the range, depending on their health. The rack is always pumped after reloading, despite the fact that this would eject a shell if any were already loaded. Like the M90 Mk I, the M90A is once again a powerful Flood weapon because of its increase in range and power, though the M90A may still require a player to shoot and melee a Flood target, depending on the type.

UNSC Remarks

 * “The kick is milder with the As—not that it was that bad to begin with—sometimes progress just seems like change, if you catch my meaning.”
 * “The adjustable stock on the M90 works just fine, but I’ve got a soft spot in my heart for the DTM/LE model—old habits die hard, I guess."
 * “Actually, I think the jury is still out on whether it means ‘STFU and STFD’ or ‘you ain’t gonna make it.”
 * “The action I saw against the Flood on Delta Halo was pretty limited—thankfully—and you would think that the M90 would be the ultimate anti-Flood weapon, right? Except that a shotgun is effective because it delivers a massive shock to a delicately balanced system of organs and the Flood don’t have that delicately balanced system of organs —it’s like shooting a mike foxtrot tree! All you can really hope to do is disassemble them as rapidly as possible in the correct order.”
 * “The shotgun is a specialist weapon—it has its uses, but they are limited. Maybe it is more accurate to call it a tool, as opposed to a weapon?”

Trivia

 * The M90 has a wide variety of slang associated with it, this includes: waste 'em, deck clearer, and universal translator.
 * In Halo: Combat Evolved and Halo 2, it is said to be a magazine fed weapon, which has caused much speculation as to whether there was a typo. This confusion is a common misconception, however, since Shotguns have an internal, non-detachable magazine which is different than the common assault weapon or sidearms magazine.
 * In Halo 3 Matchmaking there is a gametype called Shotty Snipers, where one starts with a Shotgun and a Sniper Rifle. This gametype is often verbally abused as many players use the Shotgun instead of the Sniper most of the time. There is also another gametype called "ShWATguns" in Matchmaking where one starts with only a Shotgun and has no shields.
 * In Halo: The Flood, it is stated that the M90 fires a twelve gauge shell, whereas in the Halo game manuals it states that the M90 fires an eight gauge shell.
 * You can make the shotgun reload itself in Halo: Combat Evolved, by firing 2 shots, then press fire, reload and swap it for a another weapon all at the same time. The shotgun will pump itself on the floor and will have reloaded itself.
 * In Combat Evolved, you can perform what players call the "speed pump". In this method, the player must reload the shotgun almost instantly after firing each shot. After each time he/she repeats this procedure, the shotgun will be reloaded faster than the normal rate. As a result, the shotgun will inflict a seemingly unstoppable barrage of projectiles until there are no longer any shells left to spare. This method is extremely useful in the level, The Library, as well as the remainder of the levels after it.
 * Miranda Keyes is the only known human to dual-wield a shotgun with another weapon. However, she did not fire it.
 * The M90 can also be called the "boomstick(a common name for shotguns), The Hammer, Deck Cleaner, Mop, Broom, Universal Translator, High Stick, Thunderer, Betsy, Equalizer, The Okey-47(a reference to the AK47, and many, many others" according to the Halo Encyclopedia.
 * In the Halo Legends episode The Package Kelly-087 is seen firing the M90 in semi-automatic. This suggests that the shotgun is a selective-fire weapon, or probably just overlooked, like many other things in The Package.