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Old 10-13-2006, 10:21 AM   #1
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Default Where to Aim shooting down/up?

If you're shooting uphill or downhill, how do you compensate with your rifle. I have heard 2 different thoughts on this...#1 and #2...

Say my rifle is sighted in 2" high at 100, so it's right on at 200. Shooting flat...at 25 yards the bullet path crosses the scope line and hits 2" higher at 100, then drops back down to even with the scope line at 200. Drops another 6" at 300, 18" at 400.



#1

My thought is if you're shooting uphill (let's just say a 45 degree angle), your bullet will slow down faster and drop more.

If you're shooting downhill, you bullet will not slow down as fast and will not drop as much as quickly.

In other words, if shooting uphill, 200 yards, will the bullet be dead on, or hit low?

Shooting downhill at 200 yards, will the bullet continue to rise at 150, 175 instead of dropping back to even with the scope line...causing it to hit 4" high or so at 200 yards?

How's my thinking?


#2

I've also heard something about adding or subtracting a certain percentage from the distance depending on whether it up or downhill, then shooting as if it were that distance. Anyone heard of this sort of thought?

So if it were 400 yards downhill, subtract 30%, and shoot as if it were 280...?

Okay boys...let's hear your thoughts!

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Old 10-13-2006, 10:25 AM   #2
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Default Re: Where to Aim shooting down/up?

Shooting up hill or down hill you will hit higher than if shooting the same distance on flat ground. It has something to do with gravity or angle.Don't really remember, just know it is the same up and down hill.
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Old 10-13-2006, 10:26 AM   #3
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Default Re: Where to Aim shooting down/up?

I have always been told to aim low on both uphill and downhill shots.
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Old 10-13-2006, 10:31 AM   #4
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Default Re: Where to Aim shooting down/up?

You'll be alright if you just use the horizontal distance. That is what determines the point of impact. Whether it's uphill or downhill makes no difference. As an example, if the slope is 45 degrees, either up or down, and the target is 400 yards, you would want to hold for the horizontal distance, which would be 282 yards.
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Old 10-13-2006, 10:37 AM   #5
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Default Re: Where to Aim shooting down/up?

In both cases it's the horizontal dist. component. gravity. at 45 degrees think of the 45 degree triangle 1;1;and the sq. root of two on the hypotenuse(sp?)one is the horiz. one is the elevation, you shoot farther along the hypotenuse but gravity acts on the bullet as it moves along the horizonal dist.I know it's confusing.Good luck
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Old 10-13-2006, 10:40 AM   #6
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Default Re: Where to Aim shooting down/up?

Quote:
In both cases it's the horizontal dist. component. gravity. at 45 degrees think of the 45 degree triangle 1;1;and the sq. root of two on the hypotenuse(sp?)one is the horiz. one is the elevation, you shoot farther along the hypotenuse but gravity acts on the bullet as it moves along the horizonal dist.I know it's confusing.Good luck
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Old 10-13-2006, 10:52 AM   #7
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Default Re: Where to Aim shooting down/up?

Quote:
45 degree triangle 1;1;and the sq. root of two on the hypotenuse(sp?)one is the horiz.
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Old 10-13-2006, 10:55 AM   #8
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Default Re: Where to Aim shooting down/up?

Pi divided by z2 X y= Dead Deer.
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Old 10-13-2006, 10:58 AM   #9
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Default Re: Where to Aim shooting down/up?

...what Frog and Firedog said.
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Old 10-13-2006, 10:59 AM   #10
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Default Re: Where to Aim shooting down/up?

Quote:
My thought is if you're shooting uphill (let's just say a 45 degree angle), your bullet will slow down faster and drop more.
Nothing could be farther from the truth.

That bullet doesnt know if its going up hill, or down hill, all it knows is gravity affects it the same no matter what.

The bullet speed is unchanged by uphill or downhill shooting. Measure only the horizontal distance, which on uphill or down hill is less than the actual straightline distance to the target. Since the horizontal distance is less than the actual distance when shooting on a slope, you need to hold lower for the actual distance to compensate for the shorter actual horizontal distance.

Just like shooting a bullet level out of the gun on flat ground and at the exact same time you drop a bullet from the same elevation with your hand. Both bullets will hit the ground at the same time, one will just be by your feet, and one way over there.
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Old 10-13-2006, 11:13 AM   #11
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Default Re: Where to Aim shooting down/up?

The thing to remember though, is that with any relatively flat shooting rifle, you really don't need to worry about holding low for an uphill or downhill shot, unless you're shooting at an extremely long distance and/or an extremely steep angle.
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Old 10-13-2006, 11:13 AM   #12
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Default Re: Where to Aim shooting down/up?

For all you non-math majors, there are a few companies now making range finders that will actually compensate for the uphill/downhill factor and give you the 'true' horizontal distance. I know that Leupold is one of the companies and I believe that Bushnell also has one out.
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Old 10-13-2006, 11:42 AM   #13
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Default Re: Where to Aim shooting down/up?

I don't think this is against the rules to post this here, but it's got good info on the subject.

http://www.exteriorballistics.com/eb.../article1.html
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Old 10-13-2006, 12:11 PM   #14
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Default Re: Where to Aim shooting down/up?

As others have said the effect of gravity is constant, independent of direction, all thing fall at the same rate.

The horizontal distance to the target is what your aiming for, and that's the compenent of the projectile's trajectory; gravity has an effect on, not the line of sight distance. As a result of this, you are always shooting a shorter distance that what you see.
As far as how much you should compensate. That's dependant on knowing your rifle and bullets.

I shoot archery and from understanding my bow's trajectory, I automatically compensate accordingly. I get an understanding of my bow's trajectory with my arrows from going to 3D shoot's during the summer, so by hunting season, I ready.


As a rifle hunter you should probably do something similar so you have an ideal of how much compensation at varying angles and distances.
In generally, the flatter something shoots, the less compensation is needed at a particular yardage and angle, but again this comes from knowing your equipment.
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Old 10-13-2006, 12:55 PM   #15
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Default Re: Where to Aim shooting down/up?

It's even more noticable with a slower heavier projectile.....like an arrow.

Just think of the distance between the gravitaional axis of you and the critter? Clear? :smile:

Try this http://www.leupold.com/products/rx/main.html


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Old 10-13-2006, 01:11 PM   #16
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Default Re: Where to Aim shooting down/up?

a simple way to look at it, with a 200yd zero, your point blank range will be approx 250 yds on flat level ground. on a steep up or down hill shot your point blank range will increase to approx 300yds. so put the crosshair right where you want to hit the animal and kill it, out to 300yds. if you are planning on killing game farther than 300yds, practice at the ranges you plan to shoot. a lot.
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Old 10-13-2006, 01:13 PM   #17
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Default Re: Where to Aim shooting down/up?

Quote:
The thing to remember though, is that with any relatively flat shooting rifle, you really don't need to worry about holding low for an uphill or downhill shot, unless you're shooting at an extremely long distance and/or an extremely steep angle.


If you are shooting normal hunting distance..100 to 300 yards just lay it on em and squeeze it off. Overthinking trajectory issues when the adrenalin is flowing will cause you to do crazy things in the heat of the moment and miss. Go test a few shots up and downhill at 200 yards and you will see its not all that dramatic.
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Old 10-13-2006, 01:38 PM   #18
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Default Re: Where to Aim shooting down/up?

In'em,
Yep, what the others have said....shoot 70.7% the ranged distance on a 45degree Up or Downhill shot...makes no differance if up or down. Laws of gravity are constant.

On a 22degree shot it's more like 85% or so. All this makes no differance if your zeroed at 250-300 yards though.....that is unless your Trak44 and are shooting 1000yrds.

Formula: cosine of angle x ranged distance = ballistic range. (1000yrds ranged x Cos45 = 707yrds ballistic)

if all this seems too complicated....buy one of the new laser rangefinders that do it for you. Much easier than working trigonometry just to shoot a deer. (Trak44, maybe that palm pilot might be useful for ya afterall!)
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Old 10-13-2006, 01:51 PM   #19
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Default Re: Where to Aim shooting down/up?

Boy, some of you guys sure like to complicate things.

See a deer, shoot a deer. After you figure out all the math and almost have your socks back on he runs off giggling wondering why the dumb human was just sitting there on his quad playing with his toes. :grin:
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Old 10-13-2006, 02:20 PM   #20
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Default Re: Where to Aim shooting down/up?

lol To much math. Thats why you just use an rx 2 rangerinder. It takes all the guess work out of it and tells the "true" yardage for you. lol
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Old 10-13-2006, 02:32 PM   #21
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Default Re: Where to Aim shooting down/up?

Chad, give me a break bud. I can't help myself.....I'm a ballistics junkie. :grin:

Seriously, this is important stuff if you shoot long distance. It can matter at times. Fortunately few people are presented with 45 degree 300+ shots. But say the avg guy sights his .30-06 rifle in at 100yrd and draws a E.O. tag and finds himself looking at a fine 4x4 mulie at 300 on the rim below........ he gonna miss. Why? He has no clue what the bullets will do.
Yes, this is an academic discussion, but a healthy one.
Makes a fella aware anyway.
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Old 10-13-2006, 04:51 PM   #22
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Default Re: Where to Aim shooting down/up?

Well looks like there's hope for the world as y'all have it pretty well spot on correct.

Quacka Wacka and I hopefully will get out and do some high angle shooting this spring.

If it helps- the longest horizontal distance would be if the target and yourself were on a dead level plain. In those conditions, gravity would have the maximum opportunity to affect the trajectory of the bullet.

Any angle, up or down, will only REDUCE the horizontal distance to the target. If you are zeroed at 250 yards, and you have an uphill or downhill shot at a critter that measures 250 yards line-of-sight to the target, it will have the practical affect (point of impact wise) of a shorter shot. You can still hold dead on and shoot.

The other factors, though, are that you are still taking a 250 yard line of sight shot and wind and mirage effect will still be unchanged even though the bullet drop will be less.

Vertical point of impact, less, but horizontal dispersion from wind would be the same.

regards, aw
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Old 10-16-2006, 10:09 AM   #23
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Default Re: Where to Aim shooting down/up?

Yes you are correct, Horizontal distance is what matters. With most guns, I think it is pretty safe to ignore this at anything unter 100 yards or so.
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Old 10-16-2006, 01:10 PM   #24
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Default Re: Where to Aim shooting down/up?

It all boils down to the simple question, which will hit the ground sooner when dropped from the same altitude. A pound of feathers or a pound of lead. ??? Think about that for a while and you will have the answere to all of the above.
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Old 10-16-2006, 01:34 PM   #25
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Default Re: Where to Aim shooting down/up?

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Old 10-16-2006, 02:24 PM   #26
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Default Re: Where to Aim shooting down/up?

Love the exterior ballistics page. Nice explanation on corrections. Looks like over 200 yards it does make a pretty big difference.
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Old 10-16-2006, 06:09 PM   #27
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Default Re: Where to Aim shooting down/up?

Quote:
Originally Posted by Bait O' Eggs View Post
Nothing could be farther from the truth.

That bullet doesnt know if its going up hill, or down hill, all it knows is gravity affects it the same no matter what.

The bullet speed is unchanged by uphill or downhill shooting. Measure only the horizontal distance, which on uphill or down hill is less than the actual straightline distance to the target. Since the horizontal distance is less than the actual distance when shooting on a slope, you need to hold lower for the actual distance to compensate for the shorter actual horizontal distance.

Just like shooting a bullet level out of the gun on flat ground and at the exact same time you drop a bullet from the same elevation with your hand. Both bullets will hit the ground at the same time, one will just be by your feet, and one way over there.
What BoE says is corect per any good balastic chart that deals with this kind of shot.
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