A Sniper Rifle is a type of firearm featured in the Call of Duty series designed specifically for extreme-distance precision shooting. Sniper Rifles excel at long range, where the high power, accuracy, and zoom (given by the attached scope) allow players to kill enemies at ranges other weapons would be unable to do. Sniper rifles are also one of the few weapon classes that do not lose damage over range. However, Sniper Rifles do not perform well at close range, as they have very low hipfire accuracy, long ADS times, and little peripheral vision prior to Call of Duty: Ghosts.
Sniper Rifles come in bolt-action and semi-automatic modes, and in rare cases burst fire. Bolt-action Sniper Rifles have high power, allowing for reliable one-shot kills. However, these Sniper Rifles have high recoil and a low rate of fire, due to cycling the bolt between each shot. Players tend to use sniper rifles because of convenience over long range, as most other weapons (even with high accuracy) do not have a very long range. They also tend to have a higher accuracy when aiming down the sights due to its attached scope.
Semi-automatic and burst Sniper Rifles are much more diverse than bolt-action. The semi-automatic and burst Sniper Rifles can have high power and recoil, or low power and recoil, allowing for follow-up shots if the first did not kill. Semi-automatic Sniper Rifles can be fired as fast as the user can shoot (aside from Black Ops, as all semi-automatic sniper rifles have a firecap, and the AS50 in Modern Warfare 3), unlike bolt-action Sniper Rifles.
Sniping in Modern Warfare 3 has been changed drastically. Instead of the base damage being 70 for all the sniper rifles, it has been raised to 98 (with the exception of the Dragunov and the RSASS, which are still 70). The damage multipliers for all the sniper rifles are the same, providing the same effect as previous games where some rifles would result in one shot kills from the stomach up and others would only be from the neck and head. In addition, going prone with a sniper rifle in Modern Warfare 3 has a massive benefit of reducing recoil to almost negligent amounts, allowing for rapid follow-up shots on any rifle, even the Barrett .50cal.
A noticeable change from past Call of Duty games are the sniper rifle's in Modern Warfare 3 have their base damage set at 98 by default, whereas in previous installments it was 70. This is because the Perk Stopping Power has been removed, which was key to sniping in Modern Warfare 2. This makes sniper rifles much more likely to score a one shot kill, even with a suppressor. The lower power sniper rifles (Dragunov & RSASS ) have their base damage at 70.
In Ghosts, the sniper rifles' scopes does not fill the entire screen when aiming (similarly to the Storm PSR from Call of Duty: Black Ops II); the scopes are now dual render, allowing the player to see outside the scope while aiming, although it is very blurry. Ghosts also features a new class of similar rifles: the Marksman Rifles.
Scope Glint is a weapon effect featured in most games since Call of Duty: World at War. It allows the player to better see the concealed enemies that use a sniper rifle (in most games). From time to time, their sniper scope will glint, and player can easily spot and kill them. Using an ACOG will essentially cancel the effect of scope glint.
In Call of Duty: Infinite Warfare, scope glint is featured in multiplayer at all times when a player with a sniper is aiming down sights. This puts snipers at a huge disadvantage at times because now enemies if aware can easily spot them. The only time there is no glint is when one is using the EBR-800 - Osiris epic prototype.
In Call of Duty: Ghosts, the new scoped view is only applied in multiplayer and Extinction; in campaign it still fills the whole screen like in previous games. However, this is fixed in the next-gen versions, where it is applied in campaign as well.