The ACOG (Advanced Combat Optical Gunsight) is a series of magnified weapon scopes made by the American company Trijicon. Their scopes commonly offer a magnification of 4x, meaning anything viewed down the scope will be four times bigger than when viewed normally. Usually, ACOG scopes utilize luminescent materials such as Tritium or optical fibers to improve aiming and target acquisition. The ACOG series of weapon scopes is used by the US Armed Forces, as well as parts of other nations' armies such as the British Armed Forces.
"The Advanced Combat Optic Gunsight is a medium speed, medium range scope which magnifies at 4x. A Ballistic reticle makes gauging bullet drop at longer ranges easier."
— Battlelog description
The ACOG was first seen in the Fault Line Gameplay Trailer on an M4 Carbine. It has been remodeled since the reveal, as it now has a red dot in the center of the reticle. The outside of the scope has also been remodeled, with the fiber optic visible on top, and the rear iron sight removed.
In Singleplayer, the ACOG is commonly attached to starting weapons such as the SCAR-H in Operation Guillotine. It can also be found on many weapons dropped throughout the campaign such as the F2000s in Night Shift. It gives the player an advantage of longer range targeting in aiming down the sights, but unfortunately also makes recoil unsuitable for accurate automatic fire.
The ACOG is a 4× scope like its Russian counterpart, the PSO-1. Unlike the default 8x Rifle Scope, the ACOG does not suffer from scope glint and does not need to be steadied but does have noticeable sway and recoil compared to low power optics like the Holographic sight.
The ACOG from the Fault Line series of game trailers
In Battlefield 3, when the ACOG is not aimed, the chevron can still be seen. This is most notable when the weapon is centered with the bipod.
In Battlefield 3, The ACOG reticle (like most others) lacks range finding details. The horizontal lines on a real ACOG will represent roughly the shoulder width of a man at respective ranges, shown here.