SRS99C-S2 AM sniper rifle

The Sniper Rifle System 99C-S2 Anti-Matériel (abbreviated  SRS99C-S2 AM), otherwise known as the SRS99C-S2 AM Sniper Rifle is a United Nations Space Command firearm usable in Halo: Combat Evolved and Halo Wars.

Design Details
The SRS99C is the primary Sniper Rifle used by UNSC and is featured in Halo: Combat Evolved and Halo Wars. It is, alongside its Covenant counterpart the Particle Beam Rifle, the most accurate and arguably the most powerful small-arms weapon in both arsenals. It contains a Night Vision Scope for night time accessibility. It is modular, with the scope, stock, barrel and firing mechanism capable of being swapped to match a mission profile.

Ammunition
The Sniper Rifle has one of the most advanced ammunition types in the game. It uses 14.5x114mm Armor Piercing, Fin Stabilized, Discarding Sabot rounds. These rounds are large in both length and width and are equipped with four symmetrical fins spaced equidistantly around the base of the projectile, 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 forced off of the projectile by air resistance before entering the actual target, their job having been completed.

The rounds are described as being made of very hard metal, with the core probably composed of tungsten or depleted uranium, like most anti-matériel ammunition today. The APFSDS round is an anti-matériel munition, meaning that it is specifically designed for use against military equipment rather than against other combatants. It performs rather poorly in this role, as rounds fired at vehicles and equipment will do no damage or ricochet. The round is best used on other combatants depending on their combat system (Body Armor, Energy Shields, etc). The APFSDS rounds fired by the Sniper Rifle leave behind a noticeable white vapor trail that can reveal the position of the sniper, however they can be used as an aiming aid for the sniper himself.

It's to be noted that in the Eric Nylund novels the rifle is not limited to a four round magazine size. The reason for this in the games is to ensure balanced game play. Twenty-eight rounds total (four rounds per magazine) in Halo: Combat Evolved, twenty rounds total (four rounds per magazine) in Halo 2 and Halo 3. However, in the Halo: Combat Evolved level Truth and Reconciliation you start with a Sniper Rifle and a 68 round combat load.

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 zoom (seen in Halo: Combat Evolved). The PC version has 2x and 8x, and the Halo 2 version has 5x and 10x. It is tremendously useful in its designated role, considering its extraordinary range, surpassing any other weapon of comparable size, and its incredible stopping power even against body armor and Covenant shields (i.e., those of an Elite.)

By far, its most useful application in Campaign mode is taking out the higher-ranking enemies in a group to destabilize their squad's discipline and morale. A headshot against any Covenant infantry except a Zealot, Major Domo Elites, Ultra Elites, or Hunters, results in an instant kill; Hunters fall from one shot to their unarmored torso or neck. When playing in the highest difficulty, Legendary, the Major Domo Elites will take two shots to the head and the Zealots will take three. Turning on Night Vision is done by using the flash light button

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. In competitive games between two organized teams, both will always have a sniper. Despite its obvious role, the Sniper Rifle is can be highly effective at close range in the hands of a skilled operator, as the highly damaging round is just as powerful at close range; a single round followed by a melee strike will kill a hostile almost instantly. This does not account for Flood, however, due to the body organization.

Disadvantages
The Sniper Rifle's projectile has a slight travel time at great distances, and requires practice to use effectively at range. When used in close quarters, its precision nature, slow reload time, small magazine capacity, heavy recoil, and slow rate-of-fire leave absolutely no room for error. A small combat load and the relative scarcity of ammunition available for the weapon also make it bad practice to expend ammunition on smaller, less threatening combatants, such as Grunts. It is also largely ineffective against most forms of Flood, unless the operator can land a round into the embedded infection form, or shoot combat form's limbs off at a distance.

The projectile leaves a trail that can be traced back to the sniper's location, revealing the operator's hide or drawing hostile fire. Also, the weapon is fatally ineffective against even light-skinned and unarmored vehicles (belying its designation as an anti-matériel weapon) unless a shot can be taken on the vehicle's occupants, except for Wraiths and Banshees(Banshees pilots are obviously hard to snipe, and even if you do get the opportunity to snipe the pilot, the Banshee would fly away before you could get either a clear shot or a direct hit; the Banshee pilot is invulnerable to sniper rounds anyway).

Influence
The Sniper Rifle appears to be heavily inspired by (if not directly copied from) the South African NTW-20, (most notably the Denel NTW-20), and the M107 Special Application Scoped Rifle. Many of the features present in the Halo version are included in both weapons, such as the recoil-dampening piston, the general appearance of the receiver, the magazine placement, muzzle brake and many other attributes. In addition, the round (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).

Appearances
The SRS99C-S2 AM Sniper Rifle was featured in Halo: Combat Evolved. It had a digital radar-like view which was green and had 4 knobs below the scope. It also had a longer shoulder guard. When using the telescopic sight, the weapon gives the target's range and elevation as well.

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, 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.

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 Sniper's 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 much easier.

Campaign Recommendations
Take cover behind any rock or building (if any). Easily take aim and make sure you fire before the hostile sees you. Also stick to high ground (if any). Do not waste rounds on minor threats like Unggoys (Grunts) or shield bearing Kig-Yar (Jackals) since ammo is usually scarce.

Multiplayer Recommendations
In Halo: Combat Evolved, effective use of the 99C-S2 in multiplayer takes a lot of practice. It is necessary to aim in front of a target to accommodate for server lag, how far one should aim in front depends on their angle onto the target and the amount of lag in the server. Targets are shot easiest when they are head on, moving directly toward you.

A head-shot will kill an enemy outright, regardless of shield. Night vision is best used in dark areas (obviously) but is useless in maps that have high color contrast. Good secondary weapons include the M6D Pistol which, when shot accurately dispose of an enemy in 3 shots regardless of shield. Its 2x zoom make it the perfect partner for the sniper rifle.

Use natural formations and buildings to snipe from, but move constantly and erratically (including jumping and crouching) to lower the effectiveness of counter-sniping. The fact that sniper rifle bullets leave a smoky trail is the weapons largest downside (apart from the small magazine capacity) it exposes one's position and alerts the enemy easily; constant position changing is advised to confuse the enemy. Find something to hide behind while you reload, and reload when not in a firefight. Good snipers cover teammates and kill anyone who is chasing the person on your team with the flag (note: this is only for CTF).

Sniping is easier if you turn down your look sensitivity. Unfortunately, this makes shotgun and other close quarters combat weapons slightly harder to use in a chaotic environment.

Trivia

 * Linda-058 changes the sniper's ammo size to .450-caliber in Halo: The Fall of Reach. In fact, she shoots more rounds than simply four bullets at a time.
 * In the novel Halo: Ghosts of Onyx, the Spartan-IIs and IIIs utilize grapple rounds in place of standard ammunition. These rounds are described as harpoon-like shafts attached to braided monoline rope which is coiled in a bag.
 * "Robert McLees is definitely the go-to guy for the gun stuff," says William O' Brien, part of Halo 2's animation team, "I wanted to come up with an animation for the sniper scope, an 'idle cycle'. If you activate the scope, and then sit too long without doing anything, the animation would kick in periodically, just to keep things interesting... Simple, right?... He replied, 'No way. If you adjust your scope in the field, you're dead. Snipers don't do that.' That's how detailed his weapon designs are -- not just guns, but how they work, and how a sniper would fire them. Amazing."
 * In Halo: Combat Evolved, enemy AIs do not acknowledge the Sniper Rifle's gunshot if they do not see you, despite its loud crack in close-medium quarters. If you down an enemy with the Sniper Rifle, some will note the fallen AI, but will not search for you as they would if you fired with any other weapon.
 * One possible reason that the Halo: Combat Evolved Sniper Rifle has a night-vision setting, is that, like the rest of the equipment available on board, was upgraded for the Spartans' mission. Also, Linda-058 needed specialized equipment, so the stock of snipers may have been upgraded for her.
 * In the X-Box version of Halo: Combat Evolved the maximum zoom for the sniper is 10x but in the PC version it is only 8x.
 * This version of the sniper is the only one where the user cycles the bolt after a new magazine is inserted.