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 the main UNSC close combat weapon, packing extreme firepower at close range. It can kill almost any enemy in one hit if every single pellet makes contact, and can usually kill up to three Covenant Grunts with only one blast at a similar distance. It is often wielded in urban conditions, where the tight spaces are conducive to the shotgun's wide spray. The shotgun also makes a perfect defensive weapon to fend off Covenant boarding parties inside warships, and is particularly effective against the Flood due to the tendency of Flood forms to close in and melee their targets.

Ammunition
The M90 Shotgun uses the Soellkraft 8 Gauge magnum shotgun Shell. This is an incredibly large round, not used by any modern military, but recoil has been said to be relatively low, so technology must have advanced enough to suppress the recoil. The shells have a hippo on the side in Halo: Combat Evolved. The shotgun in Halo 3 has only 6 shells per magazine, a downsize from Halo: Combat Evolved and Halo 2's 12.

Advantages
Since the Shotgun fires 15 spreading pellets per close-range shot, the combined relative force of each relatively weak pellet does a significant amount of damage. Its high damage potential makes it effective against almost any Covenant unit even the Hunter, if shot in its exposed back, but only if the player can get close enough to achieve a substantial placement of shot.

In addition, this weapon is extremely effective against all forms of Flood at short and medium ranges (depending on the model), and is capable of eliminating Combat Forms in one shot, and a group of Infection Forms with one shot also. The shotgun also reloads in a different manner than the rest of the weapons in Halo. Each round is put into the shotgun, one-by-one, so reloading all six/twelve shells at one time may take a while. However, the player may interrupt the reloading process at any time and fire with however many rounds are currently loaded into the weapon. Another popular way of firing the shotgun involves inserting a shell, firing, and then inserting another shell, etc. While this takes slightly longer, it has the advantage of always having shells chambered. Apart from that it is devastating in close combat, stronger than an Energy Sword swipe, but slightly weaker than the Energy Sword lunge, although this is the weapon to use against the Energy Sword in close combat. The only counter weapons at close range are the Energy Sword, and the Sniper Rifle. Probably one of the most effective ways to fight is to fire one shell at very close range and immediately after that, melee. You can do this by basically pressing both the right trigger and the B button at the same time with only a slight pause between pressing the buttons. The shell will usually take out your opponent's shield leaving him with basically no health and the melee will most likely kill him. It also has a small lunge ability like the sword. In addition, it is very effective to wait around corners with this weapon to kill anyone that comes around. This is an easy way to get a killing spree and shotgun spree.

Disadvantages
While highly effective at close range, at longer ranges it is rendered useless. The shotgun's pattern is extremely loose, and fans out quickly, thus at farther ranges when you fire the shotgun, only one or two pellets out of the 15 might hit. Also, the time needed to reload can make fighting at long range even more difficult due to the fact that it reloads slowly, especially without cover to hide behind. The average reload time for a Shotgun is about 9 seconds, which is 9 seconds that makes you very vulnerable and a perfect target for the enemy. As compensation for this fault, a medium or long range weapon like the Battle Rifle or the Halo: Combat Evolved M6D Pistol will make up for the Shotgun's medium to long range damage problem, and reloading can be fixed by being able to fire a shot at any time while the gun is reloading.

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 twelve 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. Despite its very slow reload rate, this is arguably the best weapon against the Flood. Players might want to duck behind somewhere just in case you need to reload. 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 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 orange fleshy openings on their armor). However, on Legendary difficulty any 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. Halo 2 Brutes also wield shotguns.

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. Many players carry the shotgun and a weapon that is very effective at medium and above ranges such as the Sniper Rifle, Covenant Carbine, M6D, or 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. On the Internet, many games are shotguns only, with most of these battles being set in the map Battle Creek or the map Rat Race. There is a move combo players commonly use with the shotgun: since the enemy players commonly are on the move when being advanced on by a foe with a "special" weapon like the Sword, Rocket Launcher, Shotgun or a vehicle, players with 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. This is most effective in Halo 3 due to the more powerful nature of both the shotgun and melee attacks. Also, if a enemy pops right up in your face, the natural way is to get close (probably close enough to touch them) and fire a shell, which, (usually) will end in a instant kill. Also, most players don't notice a shotgun in enemy hands, and will try to melee you. When they get close, they've sealed their death. If you encounter someone who snipes you since they know you have the shotgun, get a long range weapon quickly. Shotguns are useless at long range. Like the Energy Sword and the Rocket Launcher, the shotgun is often looked down upon by experienced players as a "noob weapon" due to its effectiveness in close quarter combat. The shotgun is also the only weapon to be used in the slayer variant Tower of Power. 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. Comes in handy for "shotgun combo" which is shooting then bashing immediately after. On the maps Snowbound and Epitaph, many people prefer to wait by shield doors, preparing to ambush and instantly kill those who come through.

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, while extremely powerful in close-quarters combat, is not useful at medium-range and cannot be used for long-range.

Other M90 Models

 * The DTM Series is available in 20 gauge and 10 gauge for the civilian market. The 8 gauge is only sold to law enforcement (such as the WST DTM/LE model) and military agencies.
 * The M90 series of Shotguns have another feature as well: all have a detachable stock, allowing the shotgun to be used at even closer quarters. If you look carefully at the M90, you can see that the stock is held onto the actual firearm by a "pin and button" system.
 * Only the M90A pumps the slide after reloading any number of shells. The Mk. I is only pumped reloading a full 12 shells, which is realistic. The Mk. II doesn't pump at all.

M90 Mk I
The first model presented in the Halo series, introduced in Halo: Combat Evolved and it is unarguably the strongest version. It contains 12 shells at a time, and the player could carry up to 60 more shells for a total of 72 shells. It had the longest and most realistic of the series 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 had the capabilities to take on lightly armored vehicles, such as the Ghost effectively. In the original Halo, 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. While this looks deadly, it is a medium-slow melee. 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.

The M90 Mk. I shotgun is arguably the best anti-Flood weapon in Halo: Combat Evolved. Using it, players could engage multiple Flood targets at point blank, close, and even medium range, although each individual shot's effectiveness varied greatly. However, this model shotgun was a guaranteed kill at close range, and players came to rely heavily on this weapon in the later stages of the first Halo game.

M90 Mk II
The second model, the M90 Mk II, is used in Halo 2. It changed significantly from the Mk I. Its appearance slightly changed, most notably with 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 changed as well. It could not kill targets at more than a few feet away, though a quick shoot-melee combo would usually kill an enemy very quickly. It does absolutely no damage at longer ranges. The shotgun was only very effective at very close range, and the player only carried 36 spare shells for a total of 48 shells, unlike the 72 shells like the Shotgun in Halo: Combat Evolved. Unlike the previous version, it had 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". It never cocked after reloading. It was also extremely effective against berserking Brutes.

M90A
The third model, the M90A, is used in Halo 3. 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 or 5 loads for a total of 36 shells, as opposed to the first version's 72, or Halo 2's 48 probably, like Halo 2's Mk II, this change was most likely made for balance reasons, due to the addition of the Gravity Hammer as a usable weapon. 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. This variant of the Shotgun also appears bulkier and stronger than its Halo Combat Evolved and Halo 2 relatives. The action is always cycled after reloading, despite the fact that this would eject a shell if any were already loaded. Like the Mk I M90 the M90a is once again the ultimate anti-flood weapon because of its increase in range and power, the M90A though may still require a player to shoot and melee a flood target depending on its health.

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."
 * “I believe that the sound of racking the pump of a shotgun is universally recognized as ‘kiss your ass goodbye’."
 * “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 balance 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 3, a player can make instant kills within close proximity by firing one round of a shotgun and the quickly pressing the B button to melee the vulnerable opponent. It is especially effective when used in conjunction with a Power Drain or a Bubble Shield. Also, the Shotgun, next to the Energy Sword, and Gravity Hammer, is useful for killing any known Flood form, even the Tank Form if you shoot it in the right spot. Moreover, shotgun is slightly more powerful than a Mauler. At point-blank range, a single shotgun round will kill an enemy, but from a Mauler it will only lower the opponent's shields. However, dual-wielded Maulers are stronger and more effective in close combat situation than a Shotgun, though to melee someone you have to drop a Mauler.
 * The Brute Mauler may have been developed as a direct result of brutes observing the effects of the human shotgun.
 * Brutes have rarely been seen wielding a human shotgun in Halo 3.
 * 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.
 * The UNSC uses a tube magazine, pump-action shotgun. However, semi-automatics are already far more common in modernized 21st century militaries, with some even capable of fully automatic fire or sporting detachable drum or box magazines.
 * The M90 shotgun from the Halo Universe is also very similar to the real life M90 pump action action in many ways including ammunation and variants.