ACOG Scope

The Trijicon Advanced Combat Optical Gunsights, or ACOG, is a series of optics.

In Call of Duty 4: Modern Warfare, it can be used on any Assault Rifle, Light Machine Gun, or Sub-Machine Gun after the player has unlocked all Marksman challenges for it (150 kills). It can also be used on a Sniper Rifle in lieu of its standard telescopic sight after 100 kills. Equipped as the weapon attachment, it replaces the iron sights or sniper scope and provides a 2x zoom. The increased zoom improves range rating, but introduces idle sway when aimed and hence reduces the accuracy rating. Note that effective bullet range is not affected by this attachment. The reticle is a red chevron (upside-down V), demonstrating the expected damage area of the bullet impact.

Trivia
While the ACOG does provide better shot delivery representation and enhanced zoom to weapons that don't normally have such capability, there are drawbacks:
 * When equipped and zoomed in, the weapon shakes and sways, though a patch decreased this effect.
 * It does not allow sniper rifles to be steadied.
 * The opaque surroundings of the scope blocks the player's field of view, preventing use of the minimap and written notifications.
 * It takes longer to sight through the scope (while shouldering and aiming the weapon) compared to iron sights or red dot sights.
 * The range and zoom on a sniper rifle is lowered considerably
 * When used with Steady Aim the sway of the ACOG is reduced (confirmed)
 * Aiming down an ACOG scope limits peripheral vision, and is not recommended for close quarter combat.