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How accurate are angle cosine indicators?

 
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  #8  
Old 11-26-2003, 11:27 PM
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Re: How accurate are angle cosine indicators?

Shooting a 35 degree angle at 600 yards is roughly a 540 yard shot using a cosine angle. The time of flight of the bullet will actually be longer than flat 540 yards shot.

So would you trust a cosine indicator for a shot like this?? That's the real question?


I guess I don't follow you on this one. If you range the target, the distance is the distance, regardless of the angle. Now, if you are ranging the first floor of a skyscraper from ground level and decide to shoot a pigeon at the 40th floor, now I see a change of range, but, If you have a Leica, you can range again to the bird and pow.

You also mentioned above (I don't have it in front of me) but something about the additional drop. There is no additional drop. If you are refering to the shot on an incline, that path will allways be high, though you will be hard pressed to build a gun capable of showing the difference from shot to shot. For that data you would have to provide some ballistics. Cal/Weight/BC/that sort of thing.

Now, unless I don't understand this cosine thing (I think I do) the 600 yd shot at 35 degrees relates to 491yards ground distance. I guess I have to do some reading on your gizmo you're talking about. It doesn't sound very fun to me. Shoot at stuff that doesn't run after the first round! Hehehe...
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  #9  
Old 11-27-2003, 12:14 AM
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Re: How accurate are angle cosine indicators?

OK, I see the gizmo now. Well, I can't immagine using one effectively. It seems simple enough but I don't know where in the USA you get shots at such angles, (cept NYC shooting birds). Given the way it looks, I'd find a new toy and make 2 or 3 charts as DC said. Or, just shoot a spotter.

At 680 yds, 25 degrees = 11" Bullet path variation. Thats quite a steep hill to get a foot of change mister! Same thing as a 6-12 pitch roof for 680 yards.

I think I'd hunt somewhere else.
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  #10  
Old 11-27-2003, 04:17 AM
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Location: Palmer, Alaska
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Re: How accurate are angle cosine indicators?

Jeff,

I really would like to know the answer to your question, it really buggin me too. The TOF thing I just can't work out, I do understand what you're saying though, completely. You might have just missed the thread in Equipment Reviews under cosine indicator, or something like that. TOF wasn't really discused, but it might be part of the answer to what was.

Maybe when Dave gets back from Wisconsin deer hunting he'll fix us up with an answer.

I'll call Jim Ristow and pick his brain about it tomarrow. [img]images/icons/grin.gif[/img]


* * *


Phil, Darryl,

Seems you all are in a huricane up there at that range, must be fun!

I for one, couldn't fire 10 shots in 30 seconds even if I had a 10 round magazine, let alone breathe, aim and squeeze each one off with confidence... In 3 seconds wind can do alot of differnt stuff, let alone 30 seconds, even in the predominant condition.

If you guys are keeping decent groups in a rapid fire, your conditions hold for waaaaay longer than they ever do me, I'm lucky to have 3-5 seconds most of the time. [img]images/icons/wink.gif[/img]

Are you guys suggesting reading wind is a waste of time, based on your shooting at the PA. range? Noone else has success reading wind anywhere else across the country, and they're just lucky if they repeat it and agg well with the method?

I simply don't shoot at certain ranges when I know I can't keep them all in the kill zone, that personal limit thing. And often I'm pretty limited too.

When I practice, they all stay on the target or I move closer, no point in wondering what's happing when you can know.

When we shoot in any wind, we know it can bite us if we under or over estimate, but by how much if we screw it up is the question I ask myself.

When I'm practicing, it's easy to see what range I'll need to be at to keep them all on the paper, which is usually almost twice as far away as I could keep them all in a kill zone.

I live and do most of my hunting in a 2 mile by 25 mile valley with mountains about 3-4 times as high as those, from the base, and we get wind too.

I'm kind of protected from the north wind out here 7 miles from Palmer, but I'll bet Michael is wondering if his roof is blown off about now, I heard it's blowin 50 mph in Palmer right now, not a breeze one over here though. We get the strong warm winds from the southeast through here is about all, and they get all the cold north winds.

I'm not sure "I've" got anything to really show anyone, but I would like to come see the usual 10 rounds in 30 seconds. [img]images/icons/smile.gif[/img]

What seperates the winners from the loosers at the PA. range, you make it sound as though it's just dumb luck who wins?

It does sound like an AR-10T in 243 WIN or 300 WSM might be just the ticket over there. [img]images/icons/grin.gif[/img] [img]images/icons/smile.gif[/img]

[ 11-27-2003: Message edited by: Brent ]
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  #11  
Old 11-27-2003, 07:23 AM
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Location: Pennsylvania
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Re: How accurate are angle cosine indicators?

Phil

In Colorado and up here in Cameron County, if you shoot from the bottom of the mountain to near the top or vice versa (depending on the length of the shot) you can get 20 and 30 degrees very often.

A 11" and larger drop can change the impact quite a lot if you are trying to get close to your spotter target on the first shot.


Brent.

You can only use and load "ONE" shot at a time at Williamsport or at any IBS or NBRSA range. There are no multiple rounds allowed in a magazine. That makes the 30 second Benchrest shooting that much tougher when these guys fire fast.
When the front rests are set right and you have the rear rest adjusted right (heavy guns), the return to point of aim is right there most of the time. Almost like a return to battery system.
Some of our top shooters are VERY good at the speed shooting.

Sometimes they get caught but, not that often.

That's another reason most of us here promote a sighter shot "FIRST" when Long-range hunting.
It eleminates most of the variables and allows for the killer shot (which is in a matter of 3 to 5 seconds) next to be on target.

When some wanting to make 1st round hits, won't shoot because of high winds, we are able to do so using the sighter first, method

It works everytime and we have not had to make changes between the sighter and killing shots very often unless the wind does a complete reversal and we can see that quite easily even in the 3 to 5 second window.

To us, it's a team sport and the spotter is the important person on the team.

For those of you wondering about the spotter shot first---A sighter shot is taken 100 yards in front or behind the animal and on the same level as it is standing. This in no way spooks the animal as it never relates that sound of impact to anything because it does not hear the muzzle blast at the far distance we are shooting. We are then able to make the scope corrections quickly and swing onto it for the killing shot.

Sometimes two spotters are needed first. These spotters can be made at a open patch of dirt, a dead stump base or even a small rock.
In steep mountain terrain, it works everytime.

Later and Happy Thanksgiving to all.
We are having PA wild turkey today. Makes the meal that much nicer.

DC [img]images/icons/smile.gif[/img]

[ 11-27-2003: Message edited by: Darryl Cassel ]
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  #12  
Old 11-27-2003, 10:47 AM
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Re: How accurate are angle cosine indicators?

Jeff

You don't have to read into the incline shooting as to what you may have.

You mentioned that a shot at 600 would be 540 at an angle.

What I want from my incline indicator is, how many MOA "difference" is there to the animal at the "ACTUAL" range he is at?

If an animal is ranged at 1000 yards and at 30 degrees (up or down), I want to know what the difference is I will need in MOA if he was standing on the level or zero degrees from my rifle at 1000 yards. Hence, two drop charts. You must use the rangfinder and get his range no matter what degree he is standing in the mountain or valley. "Actual" yardage from the rifle barrel to that animal is the key here.

For instance, if you run your ballistics chart at zero degrees and 1000 yards and make a drop chart, then program in 30 degrees with no other changes other then degrees, and make another drop chart then you can see the difference of MOA change you will need to make the 30 degree shot if the animal is at the same distance in any degree.

Many longrange guns will have a more or less (depending on the angle up or down) at 30 degrees of 2 MOA change from the same distance on the level.
1 MOA at 1000 yards is roughly 10" so a 20" change was made going from 1000 yards on flat land to a 30 degree shot at 1000 yards also.

Run the numbers on your program and you will know what the difference is but, make sure the range is on flat ground or at a 10, 20, or 30 degree shot and is the "SAME" in distance. The rangefinder is the important factor here to.

Later
DC

[ 11-27-2003: Message edited by: Darryl Cassel ]
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  #13  
Old 11-27-2003, 03:25 PM
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Location: McKinney TX
Posts: 403
Re: How accurate are angle cosine indicators?

Your are correct a 600 yard shot at a 35 degree angle is around 490 yards.

The point I was trying to make is the bullet will actually travel 600 yards to the target, but because of the anfle it is actually a 490 yard shot. Time of flight is almost 20 percent longer. Using a cosine only tells you the shot is 490 yards. Atleast that's how we were taught in our tactical training.

According to my RSI ballistic Lab. There is around 3 MOA (roughly 15 inches) difference between using a cosine verses calculating the angle of fire and figuring in the actual time of flight for the bullet.

I hope that makes better sense.

Anyhow, I'm off to stuff my self full of Turkey and fixen's.

God Bless everyone and I hope everyone enjoys their Thanksgiving!
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Distance is not an issue, but the wind will make it interesting!
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  #14  
Old 11-27-2003, 03:47 PM
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Re: How accurate are angle cosine indicators?

Hello again

We are saying the same thing only adding a twist to it.

When I range an animal for "actual" yardage--- A 600 yard shot at a 30 degree angle is 600 yards. When I range an animal at 600 yards on the level its 600 yards.

If you range "any" animal at a certain distance, that's how far away he is from the rifle regardless if he's on an incline or on the level ground.
It doesn't matter if he's at 35 degrees up or down or on the level. If the rangefinder says it is 1000 yards at 35 degreeas and he moves down to the level ground you are on and the rangefinder is used again on him and it still says 1000 yards, that's his distance from you.

We don't have to triangulate his position and say that if he was on the level at this distance, then that would mean that his position would be something else or a different yardage at 30 degrees. You really don't have to figure another step such as Time of Flight because a distance may be different "IF" that animal was at another position to start with.

The only thing I want to know when I shoot at an animal that is at 20 or 30 degrees up or down from my shooting spot is-----what is the MOA difference between the zero level shot and the angle shot at the "SAME" distance in yards or meters.

Maybe that's a bit clearer? [img]images/icons/smile.gif[/img]

Anyway, good shooting to you and hope you don't stuff yourself to bad that you get sick.

Later
DC

[ 11-27-2003: Message edited by: Darryl Cassel ]
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