SRS99C-S2 AM sniper rifle

The Sniper Rifle System 99C-S2 AM, more commonly known as the SRS99C-S2 AM Sniper Rifle, is a United Nations Space Command firearm used in Halo: Combat Evolved and Halo 2.

Background
The SRS99C is the primary sniper rifle used by UNSC forces, and is featured in both Halo: Combat Evolved and Halo 2. It is, alongside its Covenant counterpart, the Particle Beam Rifle, the most accurate, and arguably, the most powerful small-arms weapon in both arsenals. This rifle is closely modeled on the NTW-20 present day sniper rifle.

Advantages
The SRS99C S2 AM is designed to be used at medium to long ranges and is equipped with an electronic scope for precisely this purpose. It has two variants - one has a 2x and 10x zooms (seen in Halo: Combat Evolved) and another has a 5x and 10x zoom (seen in Halo 2). It is tremendously useful with its extraordinary range, surpassing any other weapon of comparable size, and its penetration power versus Covenant shields (i.e., those of an Elite.) By far, it's most useful purpose in campaign mode is taking out the higher-ranking enemies in a group to destabilize their squad's discipline and morale (which makes combating a larger force much easier). A headshot against any Covenant infantry except a Zealot, Major Domo Elites and Ultra Elites, Hunter, or Brute results in an instant kill; Hunters fall from one shot to their unarmored torso or neck, and many Brutes must be shot twice in the head to get past the protective helmets they often wear. When playing in the highest difficulty, Legendary, this not true. The Major Domo Elites will take two shots to the head, and the Zealots will take three. Also when the night vision function is turned on, by pressing the flashlight button (this is exclusive to Halo 1), one can see an invisible (cloaked) Elite very easily. When playing online, some players use the sniper rifle to great effect when camping. For example, skilled users may crouch inside a confined hallway and fire without the use of the scope from close range, resulting in many instant kills. And although the rifle's description claims it has a slow rate of fire, it has an actually high rate of fire for a sniper rifle. Bottom line: If you don't kill them with the first shot, then they'll bite the dust on the next one. As an added bonus, the Sniper Rifle has a fast melee speed. One can even take out an Elite or Brute in close quarters with the sniper melee (exclusive to Halo 2).

Disadvantages
Like any weapon, there is a need to lead targets if they are at extreme distances. It is hard to use at short range because its aim is so precise and it's ammo volume is so small; with only four shots, there is no room at all for error. It also has a steeper learning curve than most weapons, taking significant practice to master. Ammunition for this weapon is scarce and, because of that, it is not good practice to waste the ammo on "lesser foes" such as Grunts and Drones. It is highly ineffective against all forms of Flood and against Sentinels. The way that the sniper rifle can be effective against the Flood is if you fire at their arms, which will fall off, leaving them harmless, or if you aim directly at the tentacle protruding from the chest cavity. The bullets leave a strong visible trail that can reveal the shooter's position to others. The rifle also performs poorly against virtually all vehicles (unless a "weak spot", such as the Ghost's fuel cell, is shot). 

Tactics
The Sniper Rifle is extremely powerful, but with a small combat load, it is not good practice to use this weapon against weaker enemies (Grunts, Drones). However, the SRs penetration capabilities and superb, long range accuracy makes it excellent for killing higher ranking enemies at long range, which, in turn, disorganizes and demoralizes the enemy troops, making combat against a large ground force easier.

Campaign Recommendations
In Halo 1, try to snipe out any of the Covenant before they see you. Any Close-Quarters-Battle (CQB) weapon sill be fine for a secondary weapon. Eventually, the Covenant will notice you (if not, you're lucky! Keep on sniping until they're all dead!). Switch to your secondary weapon and kill the rest from a closer range.

In Halo 2, try to save it when you need. If you see one or two Covenant standing somewhere, save your sniper ammo and kill them with your secondary weapon (preferably a CQB weapon). A great time to snipe would be if there are lots of Covenant somewhere, then snipe them. They might not notice you until you make ONE shot, so be careful who you shoot. Run in and switch to a secondary CQB weapon and kill the rest.

Multiplayer Recommendations
In Halo 1, try to start out with a CQB weapon, and use that one to kill until you get to a great sniping spot. Try to get a Rocket Launcher to take out people if your sniping spot isn't very high. When you're all out of ammo, snipe until you win the round! It's possible, especially if there is something to hide behind while you reload.

In Halo 2, it is best to start out with a sniper instead of a CQB weapon. If you happen to respawn in a high spot, snipe people out, but watch your motion sensor to make sure no one sneaks up behind you and melees you in the back.

Effectiveness Against

 * Elites: One-hit headshot, Zealots two-hit headshot, SpecOp Elites 3-hit headshot. (Note: varies dramatically according to difficulty.)
 * Grunts: One-hit kill if headshot or bodyshots on Minor Grunts on Easy.
 * Drones: One-hit kill in all cases.
 * Jackals One hit kill for headshots and shots through the pistol opening in the shield
 * Hunters: Aim for the bright orange skin of the body. Successfully hitting this part will bring the Hunter down in one shot.
 * Brutes: 2 shots - one to knock away a helmet and one for a kill shot. Not effective for body shots.
 * Humans / Spartans (Multiplayer: Head shot is always effective unless overshield is present on a Spartan or a Elite). You can also kill the driver, passenger, or gunner of a Warthog, Ghost, or the Scorpion Tank (in the case of Halo: Combat Evolved) with a single head shot.
 * Flood: It isnt effective against any forms in Halo: Combat Evolved. This is most likely due to the fact that their flesh and bone is less dense than that of humans or Covenant. In Halo 2 a shot to the 'heart' (where there are tentacles protruding from the chest) of any Flood warrior will kill them.

Appearances
The sniper rifle was featured in both Halo: Combat Evolved and Halo 2. The original Halo's sniper rifle had a digital radar-like view which was green. It also had a longer shoulder guard. In Halo 2, the view was replaced with a visual image of the sniper's scope in real time, and had a more compact buttstock. This weapon will return in Halo 3 as a new variant known as the "SRS99D". How it behaves and other features have yet to be uncovered, although KPaul has said that it is less "magnetic," presumably making the auto-aim is less overwhelming than in Halo 2 and with a slightly slower Rate of Fire.

SRS99C-S2 AMB Sniper Rifle
The SRS99C-S2 AMB Sniper rifle is an upgrade of the SRS99C-S2 AM Sniper Rifle found and usable in Halo 2, although in Halo 2 instead of SRS99C-S2 AMB, SRS99C-S2 AM is put instead. It is properly shown to be the SRS99C-S2 AMB in Halo: Ghosts of Onyx. The upgrade consists of a new scope called Oracle N-variant Scope for accuracy and a better designed and gripped handle.

Ammunition
The Sniper Rifle has one of the most advanced ammunition types in the game. It uses Armor Piercing, Fin Stabilized, Discarding Saboted rounds. These rounds are large in both length and width, and are equipped with four symmetrical fins on the sides of the round, stabilizing its trajectory to results of amazing accuracy, with a hit ratio of 97.3%. These sabots are used to fill in the gap in the barrel to make a plug and are ripped off of the projectile before entering the actual target, their job having been completed.

The rounds are described as being made of very hard metal, so they are probably made of a skin of hardened steel or titanium, or maybe even depleted uranium (though unlikely, depleted uranium will explode when speedy contact with metal is achieved), with a hardened core of super dense tungsten. The APFSDS round is an anti-material munition, meaning that it is specifically designed for use against military equipment rather than against other combatants. The round could be used on other combatants depending on their combat system (Body Armor, Energy Shields, etc)

It's to be noted that in the Eric Nylund novels the rifle is not limited to a 4 round magazine size. The reason for this in the games is to insure balanced game play. 28 rounds total (4 rounds per magazine) in Halo: Combat Evolved, 24 rounds total (4 rounds per magazine) in Halo 2. However, in the Halo: Combat Evolved level Truth and Reconciliation you start with a Sniper Rifle that has a 68 round load.

In Halo: Combat Evolved, the APFSDS round is very powerful. On Normal Difficulties, one direct shot to the head of any Elite (i.e. Minor, Major, Zealot) will result in an instant kill.

Character Compatibility

 * Elites
 * Spartans
 * Marines
 * Drones (have animation but not used)
 * Flood Combat Form (Human)
 * Flood Combat Form (Elite)

Influence
The sniper rifle appears to be heavily inspired by (if not directly copied from) the Barrett .50 caliber rifles (most notably the Barret M82), the M107 sniper rifle, and the South African NTW-20. Many of the features present in the Halo version are included in both weapons, such as the recoil-dampening piston, the general look of the receiver, the magazine placement, muzzle brake, and many other attributes. In addition, the Sniper bullet (14.5 × 114mm) is an actual rifle cartridge, developed by the Russian Army for Anti-Tank Rifles, Heavy Machine Guns, and Sniper Rifles. However, the real 14.5 mm round has a standard cartridge design, whereas the round used in Halo is an APFSDS round (Armor-Piercing, Fin-Stabilized, Discarding Sabot).