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View Poll Results: Do you use an Angle Cosine Indicator on uphill/downhill shots?
Yes, of course! 359 24.22%
No, I don't need it where I hunt. 613 41.36%
No, but I really should use one. 510 34.41%
Voters: 1482. You may not vote on this poll

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Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

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  #15  
Unread 03-15-2011, 08:36 AM
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Join Date: Jan 2009
Location: GSP, SC, USA
Posts: 643
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

Yes, but not on my 338 yet, only got a 2% chance at anything over 300yds and I'm not geared up for anything but quick shots with Zero at 200. If I ever go Long Time-Long Range U-BET and will get the other knobs to go with it.

Made my own in 1997 from $3 worth of school supplies and a broken level's bubble, for slinging 2114s at ELK in Colorado's Weminuche Wilderness. We never got on 60 deg slopes, about 45 < 50 is all we could hold on to, but the physics of the 60yd shot on the 60deg slope requiring the 30 yd pin left me with a healthy respect for gravity at long distance.

Can't beat knowing where your projectile is going to be at all distances.
One of them " Don't Screw Around With Mother Nature things"!......
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  •   #16  
    Unread 04-23-2011, 06:07 PM
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    Join Date: Apr 2008
    Location: Philadelphia Pa.
    Posts: 403
    Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

    Just purchased a Mil Dot master comes with an angle cosine on the back of unit just need piece of string and small weight to use.
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      #17  
    Unread 04-26-2011, 01:53 PM
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    Join Date: Nov 2009
    Posts: 136
    Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

    I have and Angle Degree Indicator on mine, since my ballistic computer takes degrees and not the Cosign. I have a angle/Cosign conversion chart on my range card in my stock pack for the times when I don't have my computer with me.
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      #18  
    Unread 05-07-2011, 01:06 PM
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    Join Date: May 2009
    Location: Prosperity, Pa
    Posts: 373
    Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

    Cosine of angle
    5 deg - .4 /100 .996
    10 deg - 1.5/ 100 .985
    15 deg - 3.5/ 100 .966
    20 deg - 6 / 100 .940
    25 deg - 9.5/ 100 .906
    30 deg -13.5/100 .866
    35 deg -18 / 100 .819
    40 deg -23.5/100 .766
    45 deg -29.5/100 .707
    50 deg -35.5/100 .643
    55 deg -42.5/100 .574
    60 deg - 50 / 100 .500

    A little chart that I plastic coated and cary in my wallet. My binoculars give the angle and then I use the chart .Works for yards or meters The first column is degrees, the second is what must be subtracted for each 100 of distance. For example, a 600 yard shot at 20 degrees, would be 6 X 600 or 36 off the total. Set the scope at 600 -36 = 564. A little math is needed but sure beats guessing! The last column is the cosine and can be directly multiplied by the measured distance to give the hold distance. Using the same 600 yards X .940 = 564.
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      #19  
    Unread 06-16-2011, 04:50 PM
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    Location: California
    Posts: 174
    Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

    I use it... I Always use it... There aren't any batteries to fail; no electronics to fail, its' always right where you put it, On the Gun; and it is also in use by every military under the Nato umbrella including the US Army, US Marine Corps, US Navy, and the US Air Force.
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      #20  
    Unread 07-06-2011, 06:04 PM
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    Join Date: Jun 2011
    Location: charlo, MT
    Posts: 86
    Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

    i have always resisted anything extra to put on my rifle. the other day got a scope level and put it on my .25 " 300 WM model 70 w/lilja barrel. thought if that little item can help this one, then i would put it on all the long range guns. first 5 shot group went into the low 1's. ouch.....all you crazy guys were right.
    same for the angle indicator. always held low and never missed. only shot once over 500 yards tho. and that was about 1300 or so and got lucky and saw my impact and adjusted. so....am not going to even wait. going to get mine stat. like the android idea, several around here have one, but i hunt in areas that cell phones dont work and if it gets cold enough, the cell dont work anyway, batteries can go dead, lost, unit get broken etc. like to keep it simple.
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      #21  
    Unread 08-29-2011, 06:55 PM
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    Join Date: Dec 2002
    Location: Wyoming
    Posts: 233
    Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

    I copied this from a write up on another site. Still trying to figure what he's saying. Wish the author would've include a sample diagram. Anyone use this method? If so, how about more detail.

    "Another Rule-of-Thumb, suggested to me by Sergeant Neal Terry, a longtime
    sniper instructor and police SWAT sniper, is to draw an invisible vertical line
    through the up or down target, and where this line intersects the earth's surface,
    range it! Disregard the angle, ignore the direct distance from muzzle-to-target,
    concentrate only on adjusting elevation for the distance to where that vertical line
    touches the earth. Compensate for that distance, aim dead-on and fire. We've
    worn out several pads of paper comparing Neal's math to other kinds of up/down
    calculations - it works and it's the essence of simplicity!"
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