The "Angle Cosine Indicator" is protected by U.S. Patent 6,568,092

The "Angle Cosine Indicator," is a simple tool for hunters in mountainous terrain, and utilized to obtain their corrected for gravity distance to target. The ACI is a vault solid, water resistant precision instrument; quiet and made from aircraft grade aluminum, which is anodized in a flat black color. The Co-Sine numbers are Laser Engraved onto the body in five (5) degree increments. The lens is shatter proof, shock proof and resistant to chemicals such as acetone and cleaning solvents. Completely mechanical, there are no batteries to fail, no electronics to fail. ACI with numerals indicated in "Angle"	Battle Proven and in use by: US Marine Corps M.C.M.W.T.C. US Army, Special Forces U.S. Air Force US Navy US Border Patrol British Special Forces Canadian Special Forces Australian S.A.S. LE , Hunters and many others. - ACI with numerals indicated in "Co-Sine" ACI with numerals indicated in "Angles"
Images of User's Rifles
The "A.C.I." works on any shoulder mounted weapon system . When the weapon is held at an angle, the "A.C.I." indicates the co-sine number of that angle by means of a highly visible index mark. The co-sine number is then multiplied to the "Established Range", (sloped distance to target), or inputted into the data entry point of the users Ballistic Targeting Software, which gives you the corrected for gravity distance to target.
	There are several ways to mount the device. One way is to utilize a short, Weaver Base scope ring, which is mounted onto the scope tube, at 90 degrees. Another way is to utilize a Badger Ordinance mount designed to attach to a picantinny rail. The mount works on all day and most night scopes. Close up of the Badger Ordinance mount. Schematic of Badger Mount
Bow Hunter's using the ACI, LOVE it and so will you! When you know your true distance to target, the guesswork of where to hold is gone. It just takes a little more information to shoot expert.

How does it work? One of three ways, but simple..

a. The most accurate method is to input the cosine number into your ballistic software; i.e. Exbal Ballistic Targeting Software or Field Firing Solutions, that runs on either your home PC, Pocket PC or Palm Pilot. This is because the software takes into account the trigonomics of the fact that the bullet will still travel the full distance to target, and maintain a similar time of flight.

b. Method #2, is to multiply the cosine number to your MILRAD or MOA hold for your distance to target as indicated on your data card. For example, if your moa hold for 600 yards is 11 moa, and .87 is indicated by the ACI, you would then multiply .87 X 11moa, and obtain a corrected for gravity distance of 9.57 moa. This is fairly accurate, (Caliber Specific) although not as accurate as utilizing ballistic software. This is called the "Improved Rifleman Method."

c. Method #3, is to multiply the cosine number to your sloped distance. This will deliver the flat line distance to target, or what we call the bottom leg of the triangle.

If you experiment with your ballistic software, you will find that there can be as much as eight (8) MOA difference between method #1 and method #3. Method #1 is the most accurate & preferred method.

Now, adjust the sight elevation knob (come-ups) on your scope, for the "corrected range".

Ian's Occupied Rock & Erwin's