Advanced Combat Optical Gunsight

The Advanced Combat Optical Gunsight (ACOG) is a series of prismatic telescopic sights manufactured by Trijicon.

Some versions have an additional daytime reticle illumination via a passive external fiberoptic light pipe or are LED-illuminated using a dry battery.

[8] Some versions of the ACOG have an additional daytime reticle illumination via a passive external fiber optic light pipe.

Some ACOG models incorporate rudimentary ghost ring iron sights as a backup for targets that are within 50 m (55 yd).

[13] Although the ACOG is designed for the Picatinny rail of the M16A4 and M4, it can be mounted on the carrying handles of previous models by using a special adapter.

Only certain models of the ACOG are designed with bright enough daylight-lit fiber optic or battery-powered LED reticles that facilitate this technique.