Shooting up and down hill.


PDA






mattrobbins
October 25, 2008, 03:30 PM
Where do I aim Shooting up and down hill?

If you enjoyed reading about "Shooting up and down hill." here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
General Geoff
October 25, 2008, 03:32 PM
At the target. :neener:

mattrobbins
October 25, 2008, 03:41 PM
Gee thanks, what I meant was aim high down hill and low up hill or visa versa.

DoubleTapDrew
October 25, 2008, 03:41 PM
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.

mattrobbins
October 25, 2008, 03:45 PM
What is IIRC?

hankdatank1362
October 25, 2008, 03:45 PM
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.

General Geoff
October 25, 2008, 03:46 PM
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.

mattrobbins
October 25, 2008, 03:48 PM
thank you hankdatank1362 that helps

rcmodel
October 25, 2008, 03:51 PM
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

Hud
October 25, 2008, 03:54 PM
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

hankdatank1362
October 25, 2008, 03:55 PM
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.

hankdatank1362
October 25, 2008, 03:56 PM
BTW, Rinker's books are fantastic, especially the one you mentioned.

mattrobbins
October 25, 2008, 04:06 PM
Thanks for the advice everyone. I will look into the book mentioned also.

akodo
October 25, 2008, 04:34 PM
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.

The Bushmaster
October 25, 2008, 05:29 PM
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...

dagger dog
October 25, 2008, 08:23 PM
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!

Afy
October 25, 2008, 08:33 PM
Pythogras and Gravity

ParaElite
October 25, 2008, 08:34 PM
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.

357sigRog
October 25, 2008, 08:47 PM
I agree with dagger dog, I was always taught to aim lower when shooting up hill and down hill.

trstafford
October 25, 2008, 09:50 PM
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.

Sunray
October 25, 2008, 09:56 PM
"...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.

rangerruck
October 26, 2008, 01:40 AM
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.

Art Eatman
October 26, 2008, 12:10 PM
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.

briansmech
October 26, 2008, 12:55 PM
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.

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...

rangerruck
October 26, 2008, 02:55 PM
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.

wep45
October 26, 2008, 03:26 PM
shooting up hil....point the barrel up

shooting down hill.... point the barrel down

If you enjoyed reading about "Shooting up and down hill." here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!