The ACO (full name: Advanced Collimator Optics) is a non-magnifying red dot sight featured in ArmA 3.
Universally shared across all factions, the ACO comes with two separate variants; its NATO counterpart uses a red Bullseye reticle while the CSAT/AAF counterpart uses a green Chevron-Dot. Both variants have their zeroing set to a range of 200 m by default.
In addition, SMG variants exist for both counterparts and have reduced zeroing ranges (100 m) for use on submachine guns and other short range firearms.
- The ACO appears to be based on the "Railway" series of red dot sights manufactured by C-MORE Systems.