Long Range Hunting Online Magazine Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?
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 View Poll Results: Do you use an Angle Cosine Indicator on uphill/downhill shots? Yes, of course! 323 24.34% No, I don't need it where I hunt. 541 40.77% No, but I really should use one. 463 34.89% Voters: 1327. You may not vote on this poll

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

#29
10-09-2011, 05:39 PM
 Silver Member Join Date: Mar 2011 Posts: 125
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

Quote:
 Originally Posted by Triple BB 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!"
That method takes the horizontal component of the distance and using that for range ("rifleman" method). It could be useful in some scenarios. You could do the same thing with the Angle/Cosine indicator if you multiplied the cos of the angle against the distance ranged to target.

Some nice things about the a/c indicator, you don't need a very steep background that is nearly the same horizontal distance from you as the horizontal component of the distance of your target to you. You could multiply the cos of the angle by your moa adjustment for the direct range (see link to article below) to get a hold estimation. Finally, you could enter the angle into a good ballistics program and get a more precise model of what adjustment is needed to get on target. see - http://www.longrangehunting.com/arti...e-shooting.php

You could run some simulations using angles and the three different methods, then see what you get. Is your method getting you "close enough" to be "on target"? After all, isn't that the goal of much of this?

Hope that helps Triple BB

Here is an article with some diagrams and better explanation. http://www.longrangehunting.com/arti...e-shooting.php

Last edited by Pons; 10-13-2011 at 03:22 AM.. Reason: simplification & clarification
#30
11-27-2011, 08:16 AM
 Silver Member Join Date: May 2010 Location: Not where I would like to be Posts: 128
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

They are so easy to use and once you get used to the math you can estimate pretty darn quick
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#31
12-12-2011, 12:25 AM
 Silver Member Join Date: Nov 2011 Posts: 366
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

I bought a small inclinometer in the early 80's from a survey equipment shop.
I used it alot shooting Field tournaments and I always managed to pick up
a few points from my competitors who merely guessed how much to cut
yardage on the down hill targets. Still do as a matter of fact when I go Bow
Hunting. The new range finders with the angle built in are great.

1Hunter
#32
12-12-2011, 01:00 PM
 SPONSOR Join Date: Dec 2002 Location: California Posts: 135
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

1Hunter,

Here's the skinny on most Civilian LRF's EXCEPT for the Swarovsky.
The LRF's have the electronics or diode attached to a plastic "stick" called a gate. This plastic gate is able to be adjusted by a screw so that the diode sits centered, directly behind the lens. If you hunt in freezing temperatures, and do not keep the LRF heated, the plastic gate will react to the cold temperature and twist / warp. That will be the end of the LRF.

SWAROVSKY IS THE ONLY CIVILIAN LRF THAT I OWN. IT IS DEPENDABLE, AND THE COMPANY IS TRULY REPUTABLE. THE LRF THAT I OWN WORKS OUT TO 1837 METERS. IN MID DAY SUNLIGHT IT RANGES RELIABLY AT OR BEYOND 1500 METERS.
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#33
12-12-2011, 01:15 PM
 Silver Member Join Date: Nov 2011 Posts: 366
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

I realy like Swarovsky, especially their lens. The only thing is I
have to take a deep breath when I buy one. Usually costs a
piece of the farm. But, usually worth it.

1Hunter
#34
12-12-2011, 01:24 PM
 SPONSOR Join Date: Dec 2002 Location: California Posts: 135
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

I think that the Swarovsky LRF is under \$900.00.
IF you want one that will last you years instead of months, it's really the way to go.
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#35
12-20-2011, 10:49 AM
 Gold Member Join Date: Jul 2010 Location: Mount vernon, OH Posts: 669
Re: Do you use an Angle Cosine Indicator (ACI) for uphill/downhill shots?

Quote:
 Originally Posted by Ridge Runner CALL ME CHEAP! I use a 10 dollar angle finder from ace hardware. RR
You can also use a mil-dot master.
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