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Old November 25th, 2021, 09:17 AM #41
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Originally Posted by Doco Overboard View Post
Or is it really that a target of the same height when viewed from an angle either it be from above or below will appear to be shorter making it way easier to overshoot?
target size has nothing to do with it, other than larger being easier to hit. just consider the target being a 1" rock, it's a 1" target at whatever angle you're viewing it and at whatever angle it may be "bladed." gravity has an effect over the HORIZONTAL distance to the target, not the true distance which will be longer when the target is at an angle uphill or downhill from the shooter.
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Old November 25th, 2021, 09:22 AM #42
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Originally Posted by Striper69 View Post
You Maryland Dems kill me. Vote for Biden and the Commies then pile on to anything you can.

We're just hunting for food here. You guys are probably just hunting for your own gratification. Like the guys on tv who say they're donating the deer for hungry families.

Spare me...
wow, everyone here trying to give you the help you need and you piss on them. you're "hunting" but apparently you're not getting much actual food doing it your way. good luck with that. i'm a virginia repub by the way so you got that part wrong as well.
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Old November 25th, 2021, 10:05 AM #43
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Quote:
Originally Posted by Doco Overboard View Post
Quick question,

Or is it really that a target of the same height when viewed from an angle either it be from above or below will appear to be shorter making it way easier to overshoot?

Just say a15" target as long as it's vertical either uphill or downhill will appear to be slightly shorter for height of which, for what you see is determined by the angle it is being viewed from, than if it were to be seen from otherwise being flat.
Viewing angle does change our perception of asymmetrical target size, potentially making it look further (or closer) but bullet trajectory is another entity.
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Doesn't the target actually at around 10 degrees or so always become farther even if only very slightly dependent on range whether one is shooting uphill or downhill?
I may be misinterpreting what your saying regarding horizontal distance being different from line of sight distance?
I think it is getting hazy because you are inverting the equation, starting with the horizontal distance and then deriving the line-of-sight distance.

The basis for all of this is the Pythagorean theorem.

If you first think of the target as a matter of exact horizontal distance (leg 'b' of the triangle), THEN change the angle (modifying leg 'a' length), then yes, the line-of-sight distance (leg 'c') does increase.

If we elevate the target by 10o at 1000 yards, then our distance is *divided* by our cosine (.985), and our line of sight distance is actually 1000/.985=1015 yards.

Note that while we DID increase our line-of-sight distance as you correctly suggest, our bullet drop is still what it would be at 1000 yards even, the actual horizontal distance. As a side note, unless distances are huge, we would usually disregard a mere 10o angle. In our 1,000 yard example, the increase is only 15 yards...

Conversely, as in our examples under discussion, we are first given our line-of-sight distance (the larger figure) as we would have derived from our laser or optical/reticle ranging, and converting to horizontal distance reduces that figure. There, the formula becomes line-of-sight distance *multiplied* by the cosine.
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I'm also trying figure all the other thread discussion as well at the same time so I may be a little confused following this one.
The line-of-sight distance is what your laser tells you, but bullet's vertical trajectory is only affected by the actual horizontal distance where gravity pulls.

Think for a moment how your vertical trajectory (relative to your reticle) will not curve at all if the shot if fired straight down...effectively limiting the horizontal distance, and apparent drop, to "zero", no matter the line-of-sight distance.

Anything between "level" (max gravitational effect on vertical) and "straight down" (min gravitational effect on vertical) is going to be a gradient and some number in between max drop and no drop. We use cosine to quantify this gradient. Steeper angles have smaller cosines, approaching 'zero' (straight down), while flatter angles have larger cosines, approaching 1.0 (perfectly perpendicular to gravity).

If shooting line-of-sight distance (leg 'c' of the triangle) up/down at 45o, the cosine of 45o describes the actual horizontal distance (leg 'b' of the triangle).

The cosine for 45o is .707. If our line-of-sight distance is 1,000 yards and departure angle is 45o, gravity only gets to act on the bullet for 707 yards (1,000 x .707=707), as opposed to it's entire flight path. This causes an apparent reduction in drop that corresponds to moving the target in closer to 707 yards, a substantial change.

Because the bullet DOES travel the entire line of sight distance, wind must be calculated for the entire flight path, which is the 1,000 yard line of sight distance, even if shooting straight down.

To simply apply the cosine to distance is a traditional method called the 'Rifleman's Rule' and is a good approximation for ethical hunting distances and 'average' combat engagement distances. The error developed at very long ranges with any sort of substantial angle can cause misses if this method is used.

At true long range, errors emerge as a result of this *approximation* and we would shift to the 'scope offset method' for a much more exact solution. The scope offset method more considers actual trajectory and the important fact that the scope is not looking at the target from the same vantage point as the rifle bore.

Shooting long range matches in steep terrain, like the Allegheny Sniper Challenge, I got into the habit of exclusively using the scope offset method, wanting to tune our any error I could control. Then my misses are just a result of blowing the shot vs losing the bullet to an approximation before the trigger is pressed.
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Old November 25th, 2021, 10:19 AM #44
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Quote:
Originally Posted by Striper69 View Post
You Maryland Dems kill me. Vote for Biden and the Commies then pile on to anything you can.

We're just hunting for food here. You guys are probably just hunting for your own gratification. Like the guys on tv who say they're donating the deer for hungry families.

Spare me...
It is interesting how justifiable criticism of cruel, unethical and wasteful practices have been turned into personal attacks based on assumptions.

Your slob-hunter practices reflect badly on all of us and there is simply NO justification for what you are doing to these animals.
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Old November 25th, 2021, 10:22 AM #45
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"Scope offset method" - is there a book or web page. Google / Duckduckgo is not helpful.
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Old November 25th, 2021, 10:22 AM #46
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Quote:
Originally Posted by Striper69 View Post
You Maryland Dems kill me. Vote for Biden and the Commies then pile on to anything you can.

We're just hunting for food here. You guys are probably just hunting for your own gratification. Like the guys on tv who say they're donating the deer for hungry families.

Spare me...
Wow. You are clueless. If you are cool with causing an animal unimaginable suffering, I don't want to know you.
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Old November 25th, 2021, 10:40 AM #47
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Quote:
Originally Posted by E.Shell View Post
It is interesting how justifiable criticism of cruel, unethical and wasteful practices have been turned into personal attacks based on assumptions.

Your slob-hunter practices reflect badly on all of us and there is simply NO justification for what you are doing to these animals.
1000% this. If you're hunting an animal it is YOUR responsibility to make ethical/humane shots. Slinging lead to see what happens on a live animal isn't the way to do it. If you want to sling lead, do it on paper targets instead of animals, so you can learn how conditions change your POI.

I'm not the best shot out there, but stayed at the holiday Inn express. Unless conditions aligned perfectly, id likely never take a shot at 600 yards on a deer. And I shoot 1k+ rounds a year at 600 yards while holding 98% of those shots(NRA high master) at a 6" group.

Side note, Eds explanations of things are top notch. Makes me want to dive into the PRS/unknown distance stuff hard. We all have lots to learn in the shooting world and expanding our disciplines.
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Old November 25th, 2021, 11:54 AM #48
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Quote:
Originally Posted by whistlersmother View Post
"Scope offset method" - is there a book or web page. Google / Duckduckgo is not helpful.
The 'Scope Offset Method' the the most precise of three ways to arrive at slope solutions.

1) Rifleman's Rule: We apply the cosine to the line-of-sight distance as discussed above, resulting in correction of distance, but overlooks non-linearity in trajectory.

2) Come-Up Method: We apply the cosine to the actual come-up data, which addresses the non-linearity and is probably 'close enough' for 99% of applications.

3) Scope Offset Method: We use the come-up value, add in the distance between the scope and bore, apply the cosine correction, then take the scope offset back out. This tunes out the last factor we can account for, the scope offset, and delivers the most precise solution.

Scope Offset Method:
a) Take line-of-sight range and find your come-up value for that distance.
b) Add the distance between the scope axis and bore axis (offset).
c) Apply cosine correction.
d) Subtract the offset - this is your corrected come-up.

Example:
.308/175 M118LR equivalent with 100 yard zero
Scope height over bore 2"
Corrections in MOA
Atmospheric condition equivalent to sea level
Target at 750 yards (flat ground come-up = 24.1 MOA)
Departure angle 30o (cos=.866):

1) Rifleman's Rule:
750 x .866 = 650 yards
come-up for 650 yards = 18.8 MOA

2) Come-up Method:
750 yard come-up = 24.1 MOA
24.1 MOA x .866 = 20.9 MOA

3) Scope Offset Method:
750 yard come-up = 24.1 MOA
2" height over bore = 2" / 1.047 = 1.9 MOA
1.9 MOA + 24.1 MOA = 26 MOA
26 MOA x .866 = 22.5 MOA
22.5 MOA - 1.9 (offset) = 20.6 MOA

This method will match up to most ballistics software solutions when parameters match up.


20.6 MOA - 18.8 MOA = 1.8 MOA
1.8 MOA x 7.9" (1 MOA at 750) = 14.2" error generated using the Rifleman's Rule this far away. A low miss...
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Old November 25th, 2021, 12:04 PM #49
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Quote:
Originally Posted by Striper69 View Post
You Maryland Dems kill me. Vote for Biden and the Commies then pile on to anything you can.

We're just hunting for food here. You guys are probably just hunting for your own gratification. Like the guys on tv who say they're donating the deer for hungry families.

Spare me...
No, you're not going to start insulting people who called out a poor practice and did so with more respect than the topic deserved.
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