Angle Cosine Indicator (ACI)NATO Stock Numbers (NSNs) ACI is 1005 99 212 5621 MPN ACICOSG also 1005 01 560 0130 available right and left handed The Snipersystems 34 mm ring mount NSN is 1005992533460 MPN is ACI34MR One of the Snipersystems Essential Shooting Tools, by Global Rifle
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Snipersystems Cyclops head torch,our most popular product, just got an even better lens, and is now known as Cyclops 2.  Many customers swear by these torches as they enable them to work in the dark, thus extending their working day. Re-chargeable quality product from Global Rifle.

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Snipersystems  ZOOM Gun Light kit is £140
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rapid l.e.d. module change without tools
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Dimmer switch
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NEW Ultra long range IR module


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We manufacture under the brand name Snipersystems
Global Rifle are distributors for the following manufacturers

  • DSR rifles
  • Pfeifer-Waffen bull-pup custom rifles
  • Niedermeier rifles
  • Stradivari rifles
  • Voere rifles
  • Christensen Arms rifles
  • Schmidt and Bender and Hensoldt Military optics
  • Horusvision optics, special reticules and ballistic software
  • Shepherd and Lynx hunting scopes
  • A.R.M.S. Inc. mounts etc
  • Military night vision
  • Golight remote control lamps, searchlight and IR "Enhancer"
  • ACI, Mildot Master, Xplorer and other sniper tools
  • NiteMax digital night viewers
We also manufacture under the brand name Snipersystems
Home > Aids to accuracy

Angle Cosine Indicator (ACI)


The Angle Cosine Indicator, is a solid precision instrument, made from aircraft grade aluminium, which is anodized  in black. Its action is completely silent, it is robust and is unaffected by weather.  Above all, it is easy to use.

It is preferably attached to the scope tube at 90 degrees from the bore, by a ring mount fitted in front of, or behind the parallax adjustment knobs, depending on your eyesight preference.  The ACI works on any shoulder mounted weapon system and on almost all types of optic.  If it will not fit on your scope( eg.on some Schmidt and Bender PMIIs with adjustment turrets) then it can be fitted onto the Picatinny rail. (If the rail mount option is resorted to, it should be taken into consideration in the calculation that the eye is not seeing the cosine number straight in line with the scope tube). An ACI can be used on your scope, spotting scope, bow or binoculars.
The cosine marks go up in increments of 5 degrees starting at “0” so you can also work out the angle of the shot if you wish (making it compatible with most etched reticule based sighting systems, and also the Mildot Master).   
When the weapon is held at an angle, the ACI  indicates the cosine number of that angle by means of a highly visible index mark;  for mathematical  simplicity you should treat these marks as decimal or percentages, whichever you find easier, hence 87 would be .87 or 87%.  The "Established Range" (distance to target at the indicated angle) is then multiplied by the reading.WHAT DOES THIS DO? 
VERY IMPORTANT This can be either uphill or downhill.  The calculation is the same.
For example:  100m  x  .87 = 87 m.  Adjusted for gravity distance = 87m

Or 100 metres x  100  = 87 metres.  Same result!
Or cosine can be entered into your ballistic software. (Some software requires angle only - this can easily be counted on ACI as numbers go up and down in 5 degree increments)
WHAT NEXT?     You should now adjust sight elevation knob (come-ups) on your scope, for the "corrected range".   The ACI  has now calculated for you the distance to the target as if you were at 180 degrees to the target and automatically compensated  for gravity.  MOST IMPORTANTLY – YOU DID NOT EVEN HAVE TO BREAK YOUR CHEEK WELD. 
RESULT?  If you have done everything correctly including compensating for the wind, your shot should be
                      "Dead on Target"
This tool is supplied as standard equipment to the British Army, UK and US Special Forces, as well as to several Law Enforcement agencies.
NATO Stock Numbers (NSNs)
ACI is 1005 01 560 0130

(Also listed under 1005-99-212-5621)
The Snipersystems 34 mm ring mount
NSN is 1005992533460
The ACI  should be mounted with a ring and is available to suit optic tubes in diameter 1 inch, 30mm or 34mm.  When ordering, please select from the drop down list to suit the size of your tube .
To obtain the correct reading of the cosine numbers, the ACI should be fitted on the tube of the scope and viewed along the scope.
However, if it is not possible to fit the ACI on the scope because of illuminated turrets or mounts which get in the way, then  alternative mounts are available to fit the ACI onto the Picatinny rail. See below.
Rail Lift Mount. Use if there is space to fit

only use if ACI/ADI will not fit on tube with ring. Rail Drop Mount
One of the Snipersystems Essential Shooting Tools, by Global Rifle
Mounting solutions

Price: £167.00
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