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Shooting up and down hill.

Discussion in 'Rifle Country' started by mattrobbins, Oct 25, 2008.

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  1. mattrobbins

    mattrobbins Member

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    Where do I aim Shooting up and down hill?
     
  2. General Geoff

    General Geoff Member

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    At the target. :neener:
     
  3. mattrobbins

    mattrobbins Member

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    Gee thanks, what I meant was aim high down hill and low up hill or visa versa.
     
  4. DoubleTapDrew

    DoubleTapDrew Member

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    Depends on how far. IIRC the bullet will usually striker higher than it would if you were shooting on flat ground at the same distances. I need to find a place to practice that type of shooting myself since I hunt in canyons but sight in on flat ground.
     
  5. mattrobbins

    mattrobbins Member

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    What is IIRC?
     
  6. hankdatank1362

    hankdatank1362 Member

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    Well, you aim at the same spot, unless you're attempting hold-over.
    Always aim as if shooting the shorter distance, up or down hill.

    Imagine a right triangle formed of three lines:
    Line A, from you to the elevated or downhill target:
    Line B, a straight line from the target back to the level ground
    Line C, a line from your feet to the end of Line B where it meets the ground.

    Line C is the distance from you to your target, with respect to gravity and bullet drop.
     
  7. General Geoff

    General Geoff Member

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    If you're shooting at an extreme angle (better than 15 degrees), you'll probably have to aim very slightly low when shooting down hill, and very slightly high when shooting uphill, since gravity will be hindering the bullet's travel less or more than usual, respectively.


    edit; keep in mind this is only for longer distances, i.e. well past 300 yards for most centerfire rounds. Anything within 300 should be pretty much point of aim regardless of elevation changes to target.
     
  8. mattrobbins

    mattrobbins Member

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    thank you hankdatank1362 that helps
     
  9. rcmodel

    rcmodel Member in memoriam

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    Wrong!
    hankdatank1362 nailed it.

    In either case, you would hold lower then normal for the line-of-sight distance, because the uphill or downhill distance is less.

    Gravity only effects the bullet during the time it is in the air.

    And it is in the air less time when shooting up or down hill because the actual distance is less.

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

    rcmodel
     
  10. Hud

    Hud Member

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    What RC said.

    For up or down angles of less than 10* from horizontal, POI will not change enough to be noticable.
    A common mistake is to aim high for up-hill shots or low for down-hill shots.
    In actuallity, for shots over 10* the bullet will impact HIGHER than point of aim for BOTH up and down-hill shots depending on the angle.
    This info. is from "Understanding Firearm Ballistics" by Robert Rinker.

    Regards, Hud
     
  11. hankdatank1362

    hankdatank1362 Member

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    Here's a quickie paint sketch. While "A" may be the actual distance from you to the target, "C" is the distance you adjust your sights for. This is because this is the distance at which gravity exerts it's effect on the bullet. When people aim as if line "A" was the correct distance, that is why you end up with hits too high on the target.
     

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  12. hankdatank1362

    hankdatank1362 Member

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    BTW, Rinker's books are fantastic, especially the one you mentioned.
     
  13. mattrobbins

    mattrobbins Member

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    Thanks for the advice everyone. I will look into the book mentioned also.
     
  14. akodo

    akodo Member

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    hankdatank is correct. Gravity's pull is directional, so you need to know how far the bullet will be traveling horizontally, NOT diagonally.

    I think of it this way, when firing 500yards horizontally,the bullet is going to be 50 inches displaced from dead straight out the barrel. Now how about firing up perfectly vertically, is the bullet going to be displaced 50 inches in any direction? Of course not, perfectly vertically up, it would come down right at the gun muzzle.

    Firing vertical to the downward force of gravity is going to give you the most displacement per yard of flight.
    firing at an angle is going to cause less displacement than vertical.
     
  15. The Bushmaster

    The Bushmaster Member

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    Aiming high for up hill and low for down hill will also depend on the rifle and the range intended for that rifle. Case in point .30-30 sighted in at 100 yards and a 7mm Magnum sighted in at 300 yards. .30-30's lob them in and the 7mm Magnum has a flatter trajectory...
     
  16. dagger dog

    dagger dog Member

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    Always aim lower, but that depends on how much angle, up to and around 15 degrees the amount of under hold is minimal. Angles greater than 15 degrees require more as the distance increases.

    I too am a great fan of Robert L. Rinkers UNDERSTANDING FIREARM BALLISTICS Basic to Advanced Ballistics Simplified, Illustrated & Explained Fourth Edition. ISBN: 0-9645598-4-6 Library of Congress Catalog Card Number: 98-68591

    Published by Mulberry House Publishing
    P.O.Box 2180
    Apache Junction AZ 85217, U.S.A.

    Toll Free 1-888 738-1567


    This book should be a MUST for every shooting sports enthusiast.
    The contents explodes many of the common myths that are encountered in the pursuit of the subject!
     
  17. Afy

    Afy Member

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    Pythogras and Gravity
     
  18. ParaElite

    ParaElite Member

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    I would also get a hold of Arthur J. Pejsa's Modern Practical Ballistics. The guy is really a rocket scientist having worked on ICBMs and reentry guidance for the Space Shuttle.
     
  19. 357sigRog

    357sigRog Member

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    I agree with dagger dog, I was always taught to aim lower when shooting up hill and down hill.
     
  20. trstafford

    trstafford Member

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    Aim low gravity has less effect

    When aiming at angles approaching 45 deg or greater either up or down hill the shot will go high. Gravity is the reason that we need to shoot a trajectory and when aiming up or down there is no gravity effect on the trajectory. Ask a friend that bow hunts from a tree stand, the arrows perform the same but the effects are more noticeable due to slower arrow speed.
     
  21. Sunray

    Sunray Member

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    "...Gravity only effects the bullet..." Hey RC, put one, base down, on a table. Gravity will hold it on the table just fine. snicker. Sorry, I couldn't resist it.
     
  22. rangerruck

    rangerruck Member

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    a good rule of thumb to start with is; if you degree is more than 15 degrees, whether up or downhill, cut your holdover in half, and this is practical, all the way out to 400 yds., with a fast centerfire. a under 2900 fps centerfire, you can do that out to 300yds.
     
  23. Art Eatman

    Art Eatman Administrator Staff Member

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    Got access to Trigonometry tables? Check the cosines of angles. You'll find that until you get near 30 degrees, it doesn't really matter.

    The cosine of 45 degrees is 0.7071. That means that if the deer is 200 yards up the side of a 45-degree hill, the trajectory distance would be 140 yards. If you totally ignore the whole issue of "uphill/downhill", your error would be no more than one inch. If Bambi is at 250, you'd be able to hold almost exactly where you want to hit.

    I'm basing this on two inches high at 100 yards, which generally is dead on at 200 and about six inches low at 300. Now, that means about one inch high at 150 yards, right? And how much difference is there between 140 and 150?

    IOW, for anything under 300 or 400 yards, and angles less than 45 degrees, don't worry about it.
     
  24. briansmech

    briansmech Member

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    hunting out west like wy, nm, etc, its a little more to worry about....shots ARE typically for me >400yds, and angles can be significant. ive missed my share on misjudgements...
     
  25. rangerruck

    rangerruck Member

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    if you read my statement, and art's again, strangely they are both correct. I would still cut my hold by half, shooting up or downhill. You see, with a 200 to 250 yd zero, most fast centerfires are only going to drop about 7 inches , for another 100 yds. so if you don't cut it, according to art, and you are aiming at a deer or antelope or such, with a 7 inch target to shoot at, you are still going to hit it, in it's chest or shoulder area, if that is where you are aiming. Just maybe a little low, considering all other factors. if you aim, say, 3.5 inches high, at a shot that is 300 to 400 yds away, with a 250 yd zero, the shot will only drop about 4 inches at the 350 to 400 yd mark, which will put you , say much more at your point of aim, for the point of impact of the bullet.
    Once you get to past 400 yds, angles will really start to impact your shot placement, especially with a regular speed centerfire, such as a 30.06 or 308.
     
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