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Author Topic: Shooting at deer downhill question  (Read 1909 times)

Offline Ajj828

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Shooting at deer downhill question
« on: May 06, 2017, 02:57:08 PM »
Where I hunt it's very steep and hilly there is almost no area with flat ground. I sighted in my rifle at roughly 70 yards (I plan to go to a range before hunting season and make sure it truly is a 100 yard zero). I'm assuming most of my shots will be at a good steep angle either downhill or up hill. When shooting uphill and down hill do you have to hold your crosshairs high or low? Or do you just aim exactly where you want to hit the deer? Is it true that shooting downhill makes a flatter shot? This is my first year using a rifle so I'm not sure how rifles really shoot when it comes to elevation. I plan on going out and shooting on steep areas to test later in the summer.

Offline ghosthunter

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Re: Shooting at deer downhill question
« Reply #1 on: May 06, 2017, 03:12:44 PM »
Under 100 yards the adjustment is minimal. Just aim a little low. Up or down.

Over 100 yards a little more calculation is involved,depending on bullet and load.
There is no replacement for actual practice.

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http://millettsights.com/downloads/ShootingUphillAndDownhill.pdf

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Offline dreamunelk

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Re: Shooting at deer downhill question
« Reply #2 on: May 06, 2017, 03:45:53 PM »
What caliber?  Scope?  You may want to consider a 200 yard zero.  What distances do you think you will be shooting?

http://www.chuckhawks.com/shooting_uphill.htm

Do a search on sighting in.  Lots of info out there.

A range finder that shows true ballistic range in very helpful.

Most important practice a lot!

Offline Ajj828

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Re: Shooting at deer downhill question
« Reply #3 on: May 06, 2017, 05:47:26 PM »
What caliber?  Scope?  You may want to consider a 200 yard zero.  What distances do you think you will be shooting?

http://www.chuckhawks.com/shooting_uphill.htm

Do a search on sighting in.  Lots of info out there.

A range finder that shows true ballistic range in very helpful.

Most important practice a lot!


Tikka t3x 30-06 with a leupold vx2 4-12 50mm. I am for sure going to get myself a range finder this season. From the area I'm scouting I could easily get a 150-200 yard shot. I can't see myself getting very close to the deer like within 100 yards. I will also be looking down hill into some clear cuts so maybe 150-200 yard downhill shots. I'm using 180 grain bullets. I can't seem to find a place to sight my gun in at 200 yards. All the legal target shooting areas are 100 yards or less. I'll have to see if any local ranges have 200 yards

Offline Tbar

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Re: Shooting at deer downhill question
« Reply #4 on: May 06, 2017, 06:07:41 PM »
Aj, don't over think all of this.  Your setup is capable of all the ranges you mentioned.  If you are not going to be shooting beyond 300-350 you do not need a range finder. Your key to knowing what the ranges are will be learned at the range.  Practice! Practice! Practice!  Where are you located?

Offline Bob33

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Re: Shooting at deer downhill question
« Reply #5 on: May 06, 2017, 06:09:34 PM »
Up to 200 yards don't worry about. If you shot at a 45 degree angle at 200 yards the drop would be about the same as a shot on level ground at 140 yards. You'll mess yourself up trying to compensate worse than not doing so at those distances on big game. Sight your gun in to hit 2 inches high at 100 yards and hold dead on out to about 250 yards.
Nature. It's cheaper than therapy.

Offline jay.sharkbait

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Re: Shooting at deer downhill question
« Reply #6 on: May 06, 2017, 06:21:25 PM »
30/300

If it's less than 300 yd and or 30deg don't sweat it.


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Re: Shooting at deer downhill question
« Reply #7 on: May 06, 2017, 06:59:24 PM »
A 20 degree hill up or down is really steep.   You wouldnt think so until you put an inclinometer - rangefinder on it.  A 20 degree hill subtract 6% from your distance.   I.e  400 yards down/uphill = 376 yards.

Not that big a deal usually. Like said above 30/300 ....

Offline Ajj828

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Re: Shooting at deer downhill question
« Reply #8 on: May 06, 2017, 07:16:33 PM »
Aj, don't over think all of this.  Your setup is capable of all the ranges you mentioned.  If you are not going to be shooting beyond 300-350 you do not need a range finder. Your key to knowing what the ranges are will be learned at the range.  Practice! Practice! Practice!  Where are you located?

I think I am over thinking it. I'm just going to use a 100 yard zero and then practice 150-175 yard shots. I'm from SW Washington

Offline jay.sharkbait

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Re: Shooting at deer downhill question
« Reply #9 on: May 06, 2017, 07:24:03 PM »
Some high incline training we do at Bull Hill.

Offline Bob33

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Re: Shooting at deer downhill question
« Reply #10 on: May 06, 2017, 07:27:32 PM »
Aj, don't over think all of this.  Your setup is capable of all the ranges you mentioned.  If you are not going to be shooting beyond 300-350 you do not need a range finder. Your key to knowing what the ranges are will be learned at the range.  Practice! Practice! Practice!  Where are you located?

I think I am over thinking it. I'm just going to use a 100 yard zero and then practice 150-175 yard shots. I'm from SW Washington
You would be better off sighting in 2 inches high at 100 yards. That way you will be plus or minus 2 inches out to about 230 yards. With a 100 yard zero you will be 4 inches low at 200 yard and 6 inches low at 225 yards. :twocents:
Nature. It's cheaper than therapy.

Offline KFhunter

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Re: Shooting at deer downhill question
« Reply #11 on: May 06, 2017, 08:02:53 PM »
For live game you also need to consider bullet travel path through the target especially on extreme angles.   Shooting down you'll want the bullet to hit higher on the deer travelling down through the heart and exiting low, the opposite is true for uphill shooting.


 
« Last Edit: May 06, 2017, 08:11:33 PM by KFhunter »

Offline brew

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Re: Shooting at deer downhill question
« Reply #12 on: May 06, 2017, 08:55:53 PM »
totally agree with the last 2 posts...sight in 2" high at 100 and that will put you about dead on at 200...on steep shots you want to aim not where you want to hit on the fore side of the animal but where the bullet will exit on the aft (back) side of the animal.  with 3" of  "play" up to around 250 yards it shouldn't matter that much as long as you aim for where the buttet is going to end up rather than where the bullet hits.  my last bear was a steep down angle quartering towards my left so i put that 160 gr nosler partition high in his neck angling behind his off shoulder and he hit the ground like the carpet was pulled out from under him

Offline yakimanoob

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Re: Shooting at deer downhill question
« Reply #13 on: May 08, 2017, 04:48:10 PM »
The key points have been well covered.  If you only plan to shoot out to 200-ish yds, you have nothing to worry about.  Your 180gr bullets from a 30/06 will be travelling so fast at that range you've got nothing to worry about.  And I'll echo the previous comment that it's VERY easy to WAY over-estimate inclines in the field.  (Just think about how many fish stories you've heard about people climbing up 50-60 degree hills to get where they were).  30 degrees is quite steep and you're unlikely to encounter a higher angle than that. 

But if you're curious, the math in concept is quite simple.  From the reference of your crosshairs, your bullet will always (regardless of caliber, bullet design, muzzle velocity, air density, etc.) fall a distance (d) equal to the square of the time (t) the bullet spends traveling, times the acceleration due to gravity (g), all divided by two. In other words,  d = 0.5*g*t^2 .

If you're shooting at an angle, the acceleration due to gravity changes according to the cosine function - so if you're shooting at 30 degrees, which again is an extreme angle, the acceleration due to gravity is reduced by about 13%.  If you're shooting up (or down), gravity will slow (or speed up, respectively) your bullet according to the sine function.  So if you're shooting down at 30 degrees, your bullet will accelerate towards your target at 50% the force of gravity, or 16 feet per second squared.  This reduces your flight time and thus your bullet drops a shorter distance according to the formula above.  If you're shooting up at the same angle, your bullet will decelerate at the same rate, lengthening your flight time and thus increasing your drop. 

Simple enough in concept.  But that pesky little flight time value is a B*%CH to figure out as it depends on everything (caliber, bullet weight, air density, bullet design, muzzle velocity, etc.) and requires calculus, which is why we have ballistics calculators. 

So at the end of the day, if your shooting a 180gr bullet with a BC of .507 from a 30-06 leaving your barrel at 2750fps (standard velocity according to Nosler for their 180gr partition ammo), and you're shooting down at 30 degrees at a range of 200yds, Hornady's ballistics calculator says you'll hit 1.4 inches higher than you would if you were shooting across flat ground.  At 300yds range, that error goes up to a whopping 3.3 inches. 

QED. Ignore the math if you're shooting less than 300yds. 

Online Magnum_Willys

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Re: Shooting at deer downhill question
« Reply #14 on: May 08, 2017, 05:17:48 PM »
Its not that complicated - on phone calculator press type incline in degrees, press "cos" button, times yards.  Done.


Offline Stein

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Re: Shooting at deer downhill question
« Reply #15 on: May 10, 2017, 08:41:07 AM »
Its not that complicated - on phone calculator press type incline in degrees, press "cos" button, times yards.  Done.

Even easier, press the single button on my Vortex rangefinder.

Offline yakimanoob

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Re: Shooting at deer downhill question
« Reply #16 on: May 10, 2017, 09:56:33 AM »
Its not that complicated - on phone calculator press type incline in degrees, press "cos" button, times yards.  Done.
This would give you the vertical distance, in yards, between your target and a projected horizontal line from your position.  Why would you want to know that value in a shooting situation?

Offline yakimanoob

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Re: Shooting at deer downhill question
« Reply #17 on: May 10, 2017, 09:59:03 AM »
Even easier, press the single button on my Vortex rangefinder.
:yeah:

Modern rangefinders are wondeful.

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Re: Shooting at deer downhill question
« Reply #18 on: May 10, 2017, 10:31:31 AM »
Its not that complicated - on phone calculator press type incline in degrees, press "cos" button, times yards.  Done.
This would give you the vertical distance, in yards, between your target and a projected horizontal line from your position.  Why would you want to know that value in a shooting situation?

Sohcahtoa........    sin would give you vertical

Offline yakimanoob

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Re: Shooting at deer downhill question
« Reply #19 on: May 10, 2017, 04:16:12 PM »
Its not that complicated - on phone calculator press type incline in degrees, press "cos" button, times yards.  Done.
This would give you the vertical distance, in yards, between your target and a projected horizontal line from your position.  Why would you want to know that value in a shooting situation?

Sohcahtoa........    sin would give you vertical

True.  My mistake.  Same question though -- why would you want to know the distance of the horizontal line from you to the vertical line extending up from the deer?   

Offline Nash

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Re: Shooting at deer downhill question
« Reply #20 on: May 11, 2017, 07:59:16 AM »
Listen to The Hunt Backcountry podcast, episodes 72 and 73. Great shooting info and your question is discussed at length.

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Re: Shooting at deer downhill question
« Reply #21 on: May 11, 2017, 08:17:01 AM »
Its not that complicated - on phone calculator press type incline in degrees, press "cos" button, times yards.  Done.
This would give you the vertical distance, in yards, between your target and a projected horizontal line from your position.  Why would you want to know that value in a shooting situation?

Sohcahtoa........    sin would give you vertical

True.  My mistake.  Same question though -- why would you want to know the distance of the horizontal line from you to the vertical line extending up from the deer?

Your bullet drop is based on the horizontal range not the line of sight range - aka "True Ballistic Range" .     Your angle compensating rangefinder in its most basic design measures the line of sight distance, the angle and multiplies the cos of that angle times the line of sight distance to display your the horizontal distance.   

Offline jmscon

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Re: Shooting at deer downhill question
« Reply #22 on: May 11, 2017, 08:44:13 AM »
Gravity affects the horizontal distance, not so much the line of site. Air resistance is more constant and, if shooting down a veriticle face, would slow the bullet down to its terminal velocity. It would take a long, long distance but it would happen. Gravity affects the trajectory but air resistance is what slows the bullet down and will bring it sub sonic eventually. Gravity won't speed the bullet up, air resistance is too great.

Like some are saying, don't worry about it too much. Like bob33 said 45* slope and 200 yards line of site equate to 141 yards horizontal. That's how your bullet will be drop will act.
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Offline yakimanoob

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Re: Shooting at deer downhill question
« Reply #23 on: May 11, 2017, 11:17:18 AM »
AJ, we're veering off topic here, as we're all in agreement that at your stated range of up to around 200yds, you're better off ignoring the effect of the angle.  So if you or a mod want us to shut up, I'll gladly do so.  But until I'm told...   :chuckle:

Magnum_Willys, Jmscon, thinking in terms of the horizontal distance is incorrect, and will lead to some pretty significant error at longer ranges.  For example, say you are shooting at 500yds (along line of sight) at 30 degrees down.  In this case, the force of gravity pulling the bullet down (or more specifically, perpendicular to the LOS) is m*g*cos(30), but there is also a component of gravity pulling the bullet along the line of sight equal to m*g*sin(30).  IF the bullet were traveling in a vacuum, then this would give you the same change in drop (i.e., the difference between the drops shooting at 500yds horizontal and 433yds (500yds*cos30) horizontal would be the same difference in drop between 500yds horizontal and 500yds shooting down 30 degrees).  This change in drop, according to shooterscalculator.com and assuming the previous values of .507 BC, 180gr bullet, and 2750fps muzzle velocity, is 17.56 inches.  Meaning the bullet drops 17.56 inches less at 433yds than it does at 500yds.  In a vacuum, shooting down at 30 degrees would also cause a 17.56" reduction in drop, but because of the component of gravity pulling along the line of sight, the bullet would accelerate and arrive sooner. 

But as jmscon pointed out, we don't shoot in a vacuum (and you're 100% correct jmscon in saying the bullet wouldn't speed up -- the drag force dramatically overwhelms the small component force of gravity pulling along the LOS).  But there is still a force pulling on the bullet along the LOS towards the target equal to m*g*sin(30), which reduces flight time.  Running the ballistics computer with the same inputs as above but assuming a 30 degree down angle, we find the drop to be 45.10" at 500yds (compared to 55.10" at 500yds shooting horizontal, so the bullet drops a clean 10" less than it would have if shooting horizontal).

Long story short, if you were shooting at 500 yds down at 30 degrees, and you simply multiply your distance by cos(30) and shoot like you were shooting at 433yds horizontal, you'll be 7.56" low.  That's a pretty sizeable error and could easily lead to a missed or wounded animal.   

Offline jmscon

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Re: Shooting at deer downhill question
« Reply #24 on: May 11, 2017, 12:27:30 PM »
Here is good article: http://www.rifleshootermag.com/network-topics/tips-tactics-network/hitting-a-high-or-low-angle-shot/

Gravity is acting pirpendicular to horizontal not line of sight.

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Offline Igor

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Re: Shooting at deer downhill question
« Reply #25 on: May 11, 2017, 05:20:17 PM »

Offline yakimanoob

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Re: Shooting at deer downhill question
« Reply #26 on: May 11, 2017, 09:47:40 PM »
Here is good article: http://www.rifleshootermag.com/network-topics/tips-tactics-network/hitting-a-high-or-low-angle-shot/

Gravity is acting pirpendicular to horizontal not line of sight.

Certainly, yes, gravity always acts towards the center of the earth. When we talk about bullet "drop" when shooting at an angle, A, we're speaking in reference to the line of sight, so to figure out that drop in relation to line of sight, we have to consider how gravity is acting in relation to line of sight.

So we split the force of gravity into its component vectors, with one component equal to m*g*cos(A) acting perpendicular to the line of sight, and the other component equal to m*g*sin(A) acting along the line of sight. These two component vectors sum to equal the total force of gravity equal to  m*g acting perpendicular to horizontal as you stated.

The technique magnum_willys (and the article you posted) described only accounts for the first component that acts perpendicular to the line of sight and ignores the second vector acting along the line of sight. It also ignores the air dynamics, leading to error.

P.S., I'm simplifying by talking about line of sight. In reality these calculations are affected by the difference between line of departure (or bore line) and line of sight, especially at extreme angles or extreme distances.

P.P.S., I find it a little funny that the article dismisses velocity as having little effect on bullet flight. Tell that to everyone obsessing about muzzle velocity and talking about magnum cartridges as "flat shooting" because of all that powder.

Offline scoutdog346

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Re: Shooting at deer downhill question
« Reply #27 on: June 01, 2017, 07:17:17 PM »
What caliber?  Scope?  You may want to consider a 200 yard zero.  What distances do you think you will be shooting?

http://www.chuckhawks.com/shooting_uphill.htm

Do a search on sighting in.  Lots of info out there.

A range finder that shows true ballistic range in very helpful.

Most important practice a lot!


Tikka t3x 30-06 with a leupold vx2 4-12 50mm. I am for sure going to get myself a range finder this season. From the area I'm scouting I could easily get a 150-200 yard shot. I can't see myself getting very close to the deer like within 100 yards. I will also be looking down hill into some clear cuts so maybe 150-200 yard downhill shots. I'm using 180 grain bullets. I can't seem to find a place to sight my gun in at 200 yards. All the legal target shooting areas are 100 yards or less. I'll have to see if any local ranges have 200 yards
with that gun...if u r dead on at 100 yard shot and the buck in under 250 yards don't shoot high or low just right on. don't make things any more confusing then need be as urban normal shaking will cancel things out.  think about the longest shot u think ur going to take and figure out what u got to do then and repeat it to ur self intermittently as ur hunting or write it down on so thing u can see as ur hunting and make sure u can see it with minimal movment. but yeah man...250 or under just put the cross hares right where u want to hit.

 

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