Advanced Combat Optical Gunsight

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The United States Army fielded the TA31RCO variant of the ACOG which is designated as the M150 RCO.

Advanced Combat Optical Gunsights (abbreviated ACOG) are a series of telescopic sights manufactured by Trijicon. The ACOG was originally designed to be used on the M16 rifle and M4 carbine, but Trijicon have also developed ACOG accessories for other firearms. Models provide fixed power magnification levels from 1.5× to 6×.[1] ACOG reticles are illuminated at night by an internal phosphor. Some versions have an additional daytime reticle illumination via a passive external fiber optic light pipe or are LED-illuminated using a battery.


The ACOG is available in a variety of configurations from the manufacturer with different reticles, illumination, and other features. Most ACOGs do not use batteries for reticle illumination,[2] being designed to use internal phosphor illumination provided by the radioactive decay of tritium. The tritium illumination has a usable life of 10–15 years.[3] Some versions of the ACOG have an additional daytime reticle illumination via a passive external fiber optic light pipe. Normally this allows the brightness of the reticle to match the field of view since it collects ambient light from around the sight, although this can lead to a mismatch in lighting - such as sunlight hitting the light pipe directly, or standing in a shadow - causing the reticle to be much brighter or darker than the target.[4] Reticles have other features such as a bullet drop compensator and other different reticle shapes such as chevrons.

Some ACOG models incorporate rudimentary ghost ring iron sights as a backup for targets that are within 50 m (55 yd). Most ACOG models, when mounted to a carry handle, have an open space through the mount to allow the use of the rifle's iron sights without removing the scope.[citation needed] Others include Docter or Trijicon[5] reflex sights mounted on top.[6] The ACOG ECOS line features both of these secondary sighting systems on the same scope.

Other features include Picatinny rails,[7] flip caps, and the ability to be waterproof up to 11 m (36 ft).[8]

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.[9] Trijicon later produced ACOG mounts and adapters for weapons besides the M16, including the Beretta AR70/90 series; SIG SG 550, Heckler & Koch HK416, Bushmaster ACR, Enfield L85A2, and FN SCAR weapon systems; and the Steyr AUG.[citation needed]

Bindon aiming concept

Several ACOG models are designed to be used with the "Bindon Aiming Concept", an aiming technique developed by Trijicon founder and optical designer Glyn Bindon. The technique is essentially using the illuminated part of the reticle and its focusing rear eyepiece as a collimator sight.[10] As in any other collimator sight, the user does not actually look through the sight but instead keeps the collimated (infinity) image of the illuminated part of the reticle in focus with the dominant eye while the other eye views the entire field of view to acquire the target. In this both-eyes-open technique the brain superimposes the aiming reticle on the target. An added part of the technique is to shift focus after acquisition to the dominant eye/telescopic image for more accurate shooting. This overcomes the problem of centering or acquiring fast traversing targets common with all telescopic sights. Only certain models of the ACOG are designed with bright-enough daylight-lit fiber-optic or battery-powered LED reticles that facilitate this technique.


Related Images


Trijicon has been the subject of some criticism for inscribing a reference to a Bible verse address (JN8:12, referring to John 8:12, "I am the Light of the World") alongside the model numbers on their ACOG sights. Starting in late 2009, Trijicon began shipping sights to the U.S. military without the Bible verse.[17]

See also

  • Sight (device)
  • SUSAT, 4× telescopic sight with tritium-powered illumination similar to the ACOG


  1. "Official Listing of ACOG models". Retrieved 2011-02-11.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. - Oct 2011, Trijicon came out with a conventional battery-powered illumination ACOG [1]
  3. Tritium has a half-life of 12.5 years
  4. Tactical Handyman – ACOG Fiber Optic Fix
  5. "TA648TRD: 6x48 Trijicon ACOG". Retrieved 2010-05-23.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. "TA01NSN-DOC: 4x32 Trijicon ACOG with 7.0 MOA Docter Optic". Retrieved 2010-05-23.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  7. "TA648MGO: 6x48 Trijicon ACOG with Red Chevron Reticle and Accessory M1913 Rail". Archived from the original on 8 June 2010. Retrieved 2010-05-23. Unknown parameter |deadurl= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  8. "TA31RCO-M150CP: 4x32 Trijicon ACOG Army Rifle Combat Optic (RCO)". Archived from the original on 8 June 2010. Retrieved 2010-05-23. Unknown parameter |deadurl= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  9. FM 3-22.9 Chapter 2
  10. Jane's international defense review: IDR., Volume 34, Issues 1-6
  11. "Kit Magazine, Issue 62 Winter 2007" (PDF). Ministry of Defence. Archived from the original (PDF) on October 1, 2008. Retrieved 2008-03-16. This technology is here now! So if you see strange-looking SA80s being carried by strange-looking men, then rest assured, those users that had the requirement, had the make-over, at a price. Unknown parameter |deadurl= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. Combat Optics Reviews Trijicon ACOG TA31RCO-M4CP (USMC AN/PVQ-31B), Posted on December 17, 2010
  13. "Trijicon website". Archived from the original on 21 May 2010. Retrieved 2010-05-23. Unknown parameter |deadurl= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  14. "Picatinny hosts 2008 Type Classification and Materiel Release Awards Ceremony". Retrieved 2010-05-23.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  15. "Quantico Sentry - Marines test combat optics curriculum". 2005-10-27. Retrieved 2010-05-23.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  16. Sweeney, Patrick (2012). Gun Digest Book of the AR-15. IV. Iola, WI: F+W Media. pp. 232–233. ISBN 978-1-4402-2876-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  17. "Michigan Weapons Company Trijicon takes flak over soldiers' rifle scopes branded with Bible verses". New York Daily News. 2010-01-19.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

External links