Rifle Scopes Who uses a "Angle Cosine Indicator"

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RoninP80</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RoninP80</div><div class="ubbcode-body">if you go that route, i'd get one that reads out in "cosine", not "degrees/angle"..... that eliminates a step in the correction process/math.</div></div>How?</div></div>check it out........
http://accurateshooter.wordpress.com/2008/05/07/angle-cosine-indicator-aids-hunters/</div></div>Not exactly: With Exbal you input the angle, not the cosine. That, and it's better to use the improved rifleman's rule: multiply the dope, not the range to target.

What I meant was how does using a cosine indicator make the math easier by eliminating a step (compared to using an angle indicator)?

</div></div>

Cosine is representative of a percentage of actual traveled distance. .91 is 91% .88 is 88% etc. of your actual ditance. so if you range a target at 500 and get a cosine reading on your ACI of .90 you know to drop 10% of your range. Easily done in your head. = 450 No calculator needed in a quick engagement. Or you can use a Mildot master and find a flat plane on your rifle, set your scope to your 100 yard zero, and fight the wind blowing your string around while you or your partner breaks shooting position to read it

(setting to zero dopeyou should also do with ACI as thats where you should have zeroed the ACI) Unless you were getting .96 reading at Hawthorne because you were still on your 1000 yd dope.

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...(setting to zero dopeyou should also do with ACI as thats where you should have zeroed the ACI)</div></div>

Unnecessary. Assume that you have your scope dialed up for a 1000 yard shot, which with many .308 loads will put you in the range of 36-40 MOA.

That's two-thirds of a degree, which won't significantly affect the reading of a device like the ACI which has a resolution of 5 degrees.

Even with the Mildot Master, which has a resolution of 1 degree, being off a half degree or so in the reading is not going to create a significant error in the shot calculation, but the Mildot Master is not attached to the rifle, so that question is moot.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The string hanging from a Mildot Master is less than ideal compared to an ACI.</div></div>

I'm afraid that turns out not to be the case.

The string hanging from the Mildot Master not only can be read to a resolution of one degree, which is not the case with the ACI, but it has a longer baseline than the ACI as well.

In addition, there is no question that the plumbline on the MDM is vertical, which may or may not be the case with the ACI, depending on how accurately it was installed. You don't have to point your rifle at something to measure the angle to it, so your spotter could be doing that while you're setting up, or you could do it yourself without having to expose the rifle.

A single Mildot Master serves for every rifle I own, in addition to being much less expensive, and I'm going to carry it anyway for it's calculation abilities as well as for computing the distance to UKD targets.

I have no objection, though, to people spending money for an ACI. I like Ward Brien, the inventor. The country is in the midst of a recession, so spend away to stimulate the economy.

Just don't buy one on the belief that you're getting more for your money than you would by buying a Mildot Master. You're getting less.
</div></div>

Dont get me wrong im a big fan of the Mildot Master. Its a good multiuse tool. I have have used it to measure angles and you are correct in its accuracy. I taught and demonstrated its uses for 4 years to include the ACI. For all practical reasons if you have a properly set up and zeroed ACI and used correctly measuring angles in a combat type environment for a quick engagement its the better of the 2. I would not hesitate to use either. the mildot master would be my backup. I would in a range or benchrest environment measure with either. Just hope you have a flat surface on the rifle that is in line with the bore If you are measuring off of your tapered bore its already inaccurate. Turret will work, stock if its inline with bore. zero dope setting shold beused in all angle measuring. IMHO

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...(setting to zero dopeyou should also do with ACI as thats where you should have zeroed the ACI)</div></div>

Unnecessary. Assume that you have your scope dialed up for a 1000 yard shot, which with many .308 loads will put you in the range of <span style="font-weight: bold">36-40 MOA</span>.

That's two-thirds of a degree, which won't significantly affect the reading of a device like the ACI which has a resolution of 5 degrees.

Even with the Mildot Master, which has a resolution of 1 degree, being off a half degree or so in the reading is not going to create a significant error in the shot calculation, but the Mildot Master is not attached to the rifle, so that question is moot.

</div></div>

times that by about 10 at 1000 yards

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">times that by about 10 at 1000 yards.</div></div>

Say what? That's an incomplete sentence with no referent.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...(setting to zero dopeyou should also do with ACI as thats where you should have zeroed the ACI)</div></div>

Unnecessary. Assume that you have your scope dialed up for a 1000 yard shot, which with many .308 loads will put you in the range of 36-40 MOA

</div></div>

Times that figure by 10 at 1000

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

I stipulated the dope for a 1000 yard shot. Is there something about that you don't understand?

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...(setting to zero dopeyou should also do with ACI as thats where you should have zeroed the ACI)</div></div>

That's two-thirds of a degree, which won't significantly affect the reading of a device like the ACI which has a resolution of 5 degrees.


</div></div>

The resolution is only as good as how you read it. If its between 2 cosine values you split the difference you dont round. 5 degrees is a stretch.

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

OK - half of 5 degrees is 2.5 degrees. Having the scope dialed up for a 1000 yard shot will mean that your reading is off by a maximum of 0.67 degrees if you have 40 MOA dialed up. The error is insignificant.

Set up a 7.62X51 in a ballistics program which handles angle shots, and have it calculate the difference between a 15 degree shot and a 16 degree shot at 1000 yards. You will find that the difference is 0.2 MOA.

And the ACI was probably not zeroed to an accuracy of one degree.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I stipulated the dope for a 1000 yard shot. Is there something about that you don't understand?
</div></div>

yeah how many minutes are in 360 degrees? Just look at a clock and youll get your answer on how far off in degrees you will be from 0-40 minutes.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

military time mind you.

 

[pshell]

Re: Who uses a "Angle Cosine Indicator"

Sir, sure you know that you have more time behind the gun than I but I'm speaking from my experience. As I mentioned in my second post on this thread, I didn't go to the USMC school.

Let me cite on example from the course. Target is 835m, and reads .97 on cosine indicator. Normally, I dial 30 MOA on the gun. 30 x .97 = 29.1. 30 moa = 250.5'' of drop at 835 (30 x 8.35) 29.1 moa = 242.985 So a difference of 7.515'' at 835m. I'm shooting at a half size e-type that measures 23'' tall x12''wide. Do I need a cosine indicator to hit that? If I miscalculate the wind by more than 3 MPH I'm off at that range.

Sir, I ran my normal dope after the 2nd half of day 2 and it worked just fine. Please don't tell me that it didn't, I'm sure that you were not present. My math may be wrong at this point in the night, I'm intoxicated. Please forgive me. As I stated in my first post, under extreme circumstances I'm sure you could use one. I still will not, I'll just aim low.

 

[pshell]

Re: Who uses a "Angle Cosine Indicator"

BTW my dope for 1017m at 5500 feet is 41 moa. Shooting Corbon Match 175gr ammo from a stock Remington 700P. I'd say he is pretty close. He being Lindy.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">OK - half of 5 degrees is 2.5 degrees. Having the scope dialed up for a 1000 yard shot will mean that your reading is off by a maximum of 0.67 degrees if you have 40 MOA dialed up. The error is insignificant.

</div></div>

So you are meaning to tell me that if you are taking a shot and you manage to disturb your weapon a half of a degree while the trigger breaks that you are going to throw your round off target by 40 MOA? I dont need a palm pilot to figure out your calc is wrong. Besides ive shot in real life what we are talking about and its a double digit difference in degrees. In fact If i saw a student that was not measuring the angle right it was always the reason while they were of 7 plus degrees depending on where they had there dope upon measuring.

Think about it.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pshell</div><div class="ubbcode-body">Sir, sure you know that you have more time behind the gun than I but I'm speaking from my experience. As I mentioned in my second post on this thread, I didn't go to the USMC school. Without actually doing the math, off the top of my head at 700 yds 15% knock off is about a 100 yd dope difference.

Let me cite on example from the course. Target is 835m, and reads .97 on cosine indicator. Normally, I dial 30 MOA on the gun. 30 x .97 = 29.1. 30 moa = 250.5'' of drop at 835 (30 x 8.35) 29.1 moa = 242.985 So a difference of 7.515'' at 835m. I'm shooting at a half size e-type that measures 23'' tall x12''wide. Do I need a cosine indicator to hit that? If I miscalculate the wind by more than 3 MPH I'm off at that range.

Sir, I ran my normal dope after the 2nd half of day 2 and it worked just fine. Please don't tell me that it didn't, I'm sure that you were not present. My math may be wrong at this point in the night, I'm intoxicated. Please forgive me. As I stated in my first post, under extreme circumstances I'm sure you could use one. I still will not, I'll just aim low. </div></div>

No argument there. .97 approx 10 degrees is not indicitave of an angle shot needing much adjustment and I would do the same. I was wrong in assuming you went to the Marine school and I apologize. We have targets at .85 at our range. That raquires an adjustment.

 

[Graham]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chip8541</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">OK - half of 5 degrees is 2.5 degrees. Having the scope dialed up for a 1000 yard shot will mean that your reading is off by a maximum of 0.67 degrees if you have 40 MOA dialed up. The error is insignificant.</div></div>So you are meaning to tell me that if you are taking a shot and you manage to disturb your weapon a half of a degree while the trigger breaks that you are going to throw your round off target by 40 MOA? I dont need a palm pilot to figure out your calc is wrong. Besides ive shot in real life what we are talking about and its a double digit difference in degrees. In fact If i saw a student that was not measuring the angle right it was always the reason while they were of 7 plus degrees depending on where they had there dope upon measuring.Think about it.</div></div>Thinking: 21,600 MOA in a circle. 360 degrees. 60 MOA in a degree. 30 MOA in half a degree. 67/100 x 60 = 40.2. But the answer is: No.

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">So you are meaning to tell me that if you are taking a shot and you manage to disturb your weapon a half of a degree while the trigger breaks that you are going to throw your round off target by 40 MOA?</div></div>

You're confusing apples and oranges.

An error of a half degree in reading the <span style="font-weight: bold">angle</span> of the shot is <span style="font-weight: bold">not</span> the same thing as making a half degree error on the shot.

I didn't pick the 0.2 MOA difference on a 15 degree angle shot and a 16 degree 1000 yard angle shot out of the air - I used a ballistic program to calculate it. You might wish to do the same.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">yeah how many minutes are in 360 degrees? Just look at a clock and youll get your answer on how far off in degrees you will be from 0-40 minutes.</div></div>

As Graham noted, there are 21,600 minutes of angle in 360 degrees.

I'm afraid that you're a bit out of your depth here.

Part of the art of the rifle is being able to make good decisions about what matters and what doesn't.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chip8541</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">OK - half of 5 degrees is 2.5 degrees. Having the scope dialed up for a 1000 yard shot will mean that your reading is off by a maximum of 0.67 degrees if you have 40 MOA dialed up. The error is insignificant.</div></div>So you are meaning to tell me that if you are taking a shot and you manage to disturb your weapon a half of a degree while the trigger breaks that you are going to throw your round off target by 40 MOA? I dont need a palm pilot to figure out your calc is wrong. Besides ive shot in real life what we are talking about and its a double digit difference in degrees. In fact If i saw a student that was not measuring the angle right it was always the reason while they were of 7 plus degrees depending on where they had there dope upon measuring.Think about it.</div></div>Thinking: 21,600 MOA in a circle. 360 degrees. 60 MOA in a degree. 30 MOA in half a degree. 67/100 x 60 = 40.2. But the answer is: No. </div></div>

Graham you are correct. my clock analogy was wrong.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">So you are meaning to tell me that if you are taking a shot and you manage to disturb your weapon a half of a degree while the trigger breaks that you are going to throw your round off target by 40 MOA?</div></div>

You're confusing apples and oranges.

An error of a half degree in reading the <span style="font-weight: bold">angle</span> of the shot is <span style="font-weight: bold">not</span> the same thing as making a half degree error on the shot.

I didn't pick the 0.2 MOA difference on a 15 degree angle shot and a 16 degree 1000 yard angle shot out of the air - I used a ballistic program to calculate it. You might wish to do the same.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">yeah how many minutes are in 360 degrees? Just look at a clock and youll get your answer on how far off in degrees you will be from 0-40 minutes.</div></div>

As Graham noted, there are 21,600 minutes of angle in 360 degrees.

I'm afraid that you're a bit out of your depth here.

Part of the art of the rifle is being able to make good decisions about what matters and what doesn't.

</div></div>

yes I agree with your math it is correct. I agree ive stated some inacuracy as I am tired and ive been up all night. However, since you zero your ACI to your line of bore and if you put your scope on 1000 dope. At what point does your line of bore converge with line of sight? straight line from bore; whats the measurement in inches if you drew a straight line from bore to 1000 while sighted in at 1000 ie bullet drop. Not the line of trajectory. Im asking because im sure this is what throws it off when not on your zero dope.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">So you are meaning to tell me that if you are taking a shot and you manage to disturb your weapon a half of a degree while the trigger breaks that you are going to throw your round off target by 40 MOA?</div></div>

You're confusing apples and oranges.

An error of a half degree in reading the <span style="font-weight: bold">angle</span> of the shot is <span style="font-weight: bold">not</span> the same thing as making a half degree error on the shot.

I didn't pick the 0.2 MOA difference on a 15 degree angle shot and a 16 degree 1000 yard angle shot out of the air - I used a ballistic program to calculate it. You might wish to do the same.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">yeah how many minutes are in 360 degrees? Just look at a clock and youll get your answer on how far off in degrees you will be from 0-40 minutes.</div></div>

As Graham noted, there are 21,600 minutes of angle in 360 degrees.

I'm afraid that you're a bit out of your depth here.

Part of the art of the rifle is being able to make good decisions about what matters and what doesn't.

</div></div>

Im wondering if the optical offset is the culprit. Mathmatically you are in more depth than I at the moment. Wondering if you can explain it because it does happen. I know its worse the steeper the angle as well. In practice I am not out of depth with the 100 yd dope to measure. Ive set it on both and measured the difference multiple times multiple ranges and it is definitly more than .6 degrees

 

[Lowlight]

Re: Who uses a "Angle Cosine Indicator"

Dude arguing Math with Lindy is a lesson in futility, aside having been a combat Marine before you were born, he hold more degrees than you have numbers in your MOS...

I would hang it up, and take his word for it, his math is spot on and he knows a thing or two beyond slinging some lead and calling it a hit without the how or why like the military does.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Dude arguing Math with Lindy is a lesson in futility, aside having been a combat Marine before you were born, he hold more degrees than you have numbers in your MOS...

I would hang it up, and take his word for it, his math is spot on and he knows a thing or two beyond slinging some lead and calling it a hit without the how or why like the military does. </div></div>

I gather that from the short time I got to talk to him for sure.

I just know ive seen this consistently. The USMC isnt the only ones to teach the dope point either. 10th Group, Civilian, Quantico etc. I am now conceding to his abilities but invite him to check it practically. It does have an effect, and im hoping to see if he can explain it mathematically to me. His math makes perfect sense (of course) but something somewhere is missing and I gather he would be more qualified to find the missing bit of the equation.

Ill have to admit i was starting to grab at straws to try to explain it Just hoping he could explore it further.

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

I'm going to provide you an additional explanantion on why minor errors in measuring the angle on a shot make no practical difference, but the point to take away from this is not why that is, but that <span style="font-style: italic">they make no difference.</span>

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">However, since you zero your ACI to your line of bore and if you put your scope on 1000 dope. At what point does your line of bore converge with line of sight? straight line from bore; whats the measurement in inches if you drew a straight line from bore to 1000 while sighted in at 1000 ie bullet drop. Not the line of trajectory. Im asking because im sure this is what throws it off when not on your zero dope.</div></div>

Assume that you did what you say above, i.e., you zeroed the ACI to the line of the bore.

Let's further assume that you have your scope zeroed at 100 yards.

There are two angular components to a short-range - say, 100 yard - zero.

One is compensation for the height of the scope over the bore. That angle may be computed as:

angle = arctan (height above bore/distance to target)

In the case of my AI, for example, with a height above bore of 1.75 inches, at 100 yards (3600 inches) it's:

angle = arctan(1.75/3600) = .03 degrees or 1.67 MOA

The other component is the drop from the muzzle to the zero range. With my load at 100 yards, that's about 2.7 inches, or, using the same formula above, about 2.58 MOA.

Add those two up, and it's about 4.25 MOA or about 1.25 mil.

Which is probably more than anyone really wanted to know. But that's the amount of elevation which is consumed by a short range zero, which the interested readers, if there are any, can compute for their own setup.

Now, my point is that your line of sight on the scope is already off from the line of the bore by that amount - but it's an amount that makes no difference.

I seriously doubt that you or anyone else have a rigorous method for aligning the ACI with the line of the bore which is accurate to one degree.

Nor is it necessary to develop one, which certainly could be done.

It's not necessary because a slight error makes no difference, as I've already demonstrated by calculating the difference a one degree measurement error makes on a 1000 yard shot, i.e., an error so small that you can't hold it - and we're talking about errors smaller than that.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The USMC isnt the only ones to teach the dope point either. 10th Group, Civilian, Quantico etc</div></div>

Several sniper publications, including early editions of the Marine Corps Sniper Manual and the book <span style="font-style: italic">The Ultimate Sniper</span>, taught that increasing humidity in the air increased drag, which resulted in a lower point of impact unless compensated for. That was wrong, too.

The art of the rifle includes making good distinctions about what matters and what doesn't.

Small errors in measuring the angle of a shot make no difference.

I hope that we're done here.

 

[strick9]

Re: Who uses a "Angle Cosine Indicator"

Lindy,
Does your noggn ever hurt? Right now mine does glad to have folks like ya round.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: STRICK9</div><div class="ubbcode-body">Lindy,
Does your noggn ever hurt? Right now mine does glad to have folks like ya round. </div></div>

Ill have to agree, and ill eat my crow. I feel like Matt Damon just told me "how do you like them apples". Thanks for being patient with a stubborn ass like me. Just measured albeit a very close target (water bottle lid on the floor) with a slope doper off of a chair, and low and behold half degree difference. Somehow somewhere ive been wrong all these years.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

You learn something every day.

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

I have an engineering degree, and enjoyed a career in that field, which I am grateful to have retired from. That left me with some skills in analyzing problems with mathematical tools.

However, the key skill in engineering - as opposed to theoretical science - is learning to judge what matters, and what doesn't, in order not to lose sight of the ultimate objective, which, in shooting, is <span style="font-style: italic">hitting the target.</span>

For a funny example of what happens from paying attention to stuff which doesn't matter - and why I list my degree in electrical engineering before the one in computer science, see:

The Difference

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I have an engineering degree, and enjoyed a career in that field, which I am grateful to have retired from. That left me with some skills in analyzing problems with mathematical tools.

However, the key skill in engineering - as opposed to theoretical science - is learning to judge what matters, and what doesn't, in order not to lose sight of the ultimate objective, which, in shooting, is <span style="font-style: italic">hitting the target.</span>

For a funny example of what happens from paying attention to stuff which doesn't matter - and why I list my degree in electrical engineering before the one in computer science, see:

The Difference

</div></div>

I agree. There is a ton of minutia details that effect it but not enought to miss body size targets. I had for sure thought what we were talking about made more of a difference than it actually does. Cant wait to get home and throw some rounds at the whole theory to retrain myself out what ive previously believed.

As a side note I do level my rifle off of the scope turret while I slip scales on the ACI. Dont know how accurate it is but it seems to work out ok. Probably off a degree or so.

 

[chip8541]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I have an engineering degree, and enjoyed a career in that field, which I am grateful to have retired from. That left me with some skills in analyzing problems with mathematical tools.

However, the key skill in engineering - as opposed to theoretical science - is learning to judge what matters, and what doesn't, in order not to lose sight of the ultimate objective, which, in shooting, is <span style="font-style: italic">hitting the target.</span>

For a funny example of what happens from paying attention to stuff which doesn't matter - and why I list my degree in electrical engineering before the one in computer science, see:

The Difference

</div></div>

Ha! complex solutions to simple problems. Good read.

 

[DaveV]

Re: Who uses a "Angle Cosine Indicator"

Hey Lindy,
Are you up for an article on your site with this topic?

Kinda a "Lindy sticky"

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

Sierra has covered the inclined shooting subject much better than I can.

About the only thing of much significance you can take away from this discussion is that what you measure the angle with just doesn't matter that much.

 

[DaveV]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Sierra has covered the inclined shooting subject much better than I can.

About the only thing of much significance you can take away from this discussion is that what you measure the angle with just doesn't matter that much.</div></div>

Roger that. One question remains for me, what about the thoughts on the ACI being faster for a snap shot? Could have good hunting application.

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

If you're concerned about an angled snap shot at typical hunting ranges, just hold a little low. But not much.

If you're really concerned about how low, just experiment with a ballistic program at the angles and ranges you think you're likely to encounter.

One of the best uses of a ballistic program is to explore error margins.

 

[utnapishtim]

Re: Who uses a "Angle Cosine Indicator"

I still have what may be a silly question. If I install an ACI on a scope that is on a 20moa base, will that throw off the result that the ACI displays? My simpleton logic tells me that it would, and then and application of the reading against the dope would be wrong. Am I way off here?

 

[Lindy]

Re: Who uses a "Angle Cosine Indicator"

If you read back through this thread, you will find a demonstration that errors in reading that angle of one degree will not materially affect the calculation of a shot.

The inclination of a 20 MOA base is a third of one degree.

You may, therefore, ignore that potential source of error.

The art of the rifle is based upon making distinctions between what matters and what does not matter to the objective of hitting the target.

 

[Ratbert]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">
The art of the rifle is based upon making distinctions between what matters and what does not matter to the objective of hitting the target.
</div></div>

You really should consider changing your signature to this, Lindy, given then amount of time you spend addressing the issue.

 

[Deleted member 10043]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: azimutha</div><div class="ubbcode-body">Yep, as Lindy said (and I mentioned above): You've either got to multiply your drop or your come-up to get the adjustment (and it will be very close then to what you can get with a ballistics program). </div></div>

Okay, lets see if I got the above correct with some added variables. I've lasered a target at 700 yards. The CSI shows a cosine number of 90. I'm using a Ballplex reticle and aiming with the 500 yard reference line, which is 12 MOA or -92.27" drop at that range reticle reference line for the ammo I'm using.

-92.27 * .90 = -83"

If I'm using the MilDot Master correctly, I'm showing 11.5 MOA for -83" at 700 Yards. So, instead of the 12 MOA per Ballplex chart I use 11.5 MOA per ACI and MilDot Master?

Just multiplying the known 700 laser yardage by the cosine number I get 630 yards, which amounts to about 7.75 MOA per Ballplex chart. That's a difference of 3.75 MOA


So, if correct, does the 11.5 MOA come close to the ballistic software people are using? I'm following this correctly, right?


BTW, 11.5 MOA translates to about 690 yards. A 10 yard difference from the lasered 700 yards.

 

[Oddball Six]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BMG50CAL</div><div class="ubbcode-body">Who uses a "Angle Cosine Indicator" for shooting </div></div>

I do.

It just makes life a little bit easier in colorado. Everything around here is sloped some which way.

 

[Deleted member 10043]

Re: Who uses a "Angle Cosine Indicator"

I'm making it more confusing than it needs to be. Multiply the bullet drop by the cosine number and then cross reference to a range chart to get slant yardage and MOA. Simple enough.

 

[robozebra]

Re: Who uses a "Angle Cosine Indicator"

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">If you read back through this thread, you will find a demonstration that errors in reading that angle of one degree will not materially affect the calculation of a shot.

The inclination of a 20 MOA base is a third of one degree.

You may, therefore, ignore that potential source of error.

The art of the rifle is based upon making distinctions between what matters and what does not matter to the objective of hitting the target.
</div></div>

I was wondering this same question as I read through this thread, and my guess was that it was such a small angular "error" that it was insignificant. Glad you agree Lindy. BTW, I'm always impressed with your explanations Lindy. Hopefully one of these days we'll cross paths and I can pick your brain about shooting. I love the math associated with this sport. That's actually one of the things that got me interested in shooting sports. I'm such a nerd...

CWJ

 

[BrokenSailor]

Re: Who uses a "Angle Cosine Indicator"

All of you guys involved in this discussion saved me a lot of questions about the ACI, the ASLI, or just staying with my Mildot Master. Thanks for taking the time to talk out the points. It was very educational.

 

[longguntoter]

Re: Who uses a "Angle Cosine Indicator"

Wow, I feel way behind the curve. I don't even know what that is.

 

[elkstalker338]

Re: Who uses a "Angle Cosine Indicator"

I have one I would sell someone, 75 bucks plus shipping

 

[427Cobra]

Re: Who uses a "Angle Cosine Indicator"

This ain't the for sale section, cya