Call of Duty has two firing modes that players utilize on the battlefield. The first is shooting from the hip. This is a much more inaccurate mode of firing, but it can save you when an enemy is right on top of you. The second mode of firing is called Aiming Down Sight, or ADS.
ADS provides players with greater accuracy in exchange for vision. While players are aiming down sight, their peripheral vision is blocked somewhat. Aiming down sight also takes a small bit of time to bring the weapon’s sights to your eyes. Red Dot Sight attachments are the simplest versions of sights that offer minimal zoom but are fast to use.
Guns with attachments that reduce mobility make aiming down sight take a greater amount of time. Some sights like the Thermal Optic (pictured below) are slow to use as well and are better suited for long-range engagements. Having this sight up close can cause you to lose quick gun battles, which are often seen in Call of Duty matches.