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# Up & Down hill shooting?

#1
09-18-2003, 10:37 AM
 Silver Member Join Date: Jun 2003 Location: Aussie in Italy Posts: 433
Up & Down hill shooting?

Looking around my place for a spot to shoot 500 - 1000m, I found that anywhere I have that kind of extension also has a fair amount of elevation difference, mostly downhill.

I just saw for the first time a "slope dope" card in a sniper site.

How do you calculate for this kind of shooting?
#2
09-18-2003, 10:48 AM
 Platinum Member Join Date: May 2001 Location: Pennsylvania Posts: 1,757
Re: Up & Down hill shooting?

Look at any ballistic program I know of and it will have a "slope" angle for you to program in, concerning the angle in degrees you are shooting.

The bullet will shot higher either "UP OR down" angle from a level sight in at your club range.

Later
DC
__________________
Darryl Cassel
#3
09-18-2003, 10:59 AM
 Writers Guild Join Date: Jul 2001 Posts: 1,459
Re: Up & Down hill shooting?

How to you feel about trigonometry? The bullet only cares about the horizontal component of distance to the target. So if your backstop is downhill, you will need to find one that is further away then the range you want to shoot.

If my math is correct, that would be range distance desired divided by Cos(angle of declination)times visual distance.

R = cos(deg) X line of sight distance downhill.

Jerry
#4
09-18-2003, 01:58 PM
 Platinum Member Join Date: May 2001 Location: Pennsylvania Posts: 1,757
Re: Up & Down hill shooting?

Aussie

If your taking "LONG" shots just take a spotter shot first and it will eleminate any downhill or uphill "mystery."

You could have drop charts for every 10 degrees that you are shooting or I have a protractor and level attached to the side of my 338/416 that gives me the degrees I'm shooting. I look at the series of drop charts for the degrees I'm shooting and it works out fine.

The "BEST" method for us though, is to take the spotter shot first and correct to the impact.

At the ranges we shoot, theres to many variables to try for one shot hits. We want a kill shot when we go after that animal and not a wounding situation which can easily occur from 1250 yds to 2100 yards and further.

At 500 yds to 750 yards it's a different ballgame entirely. One shot kills are routinely made even with uphill and downhill shots.
Practice shooting the angles you think you will be hunting in and see what the rifle does. You can make up your own actual fire drop charts.

Later
DC
__________________
Darryl Cassel
#5
09-18-2003, 02:25 PM
 Silver Member Join Date: Jun 2003 Location: Aussie in Italy Posts: 433
Re: Up & Down hill shooting?

I was scouting for spots to set up for practice. Therefore I could easily learn exantly how the rifle performs, I was just curious to learn a bit about the mechanics of the phenomonon.

Which you guys have done a fine job of describing. Thanks.
#6
09-18-2003, 11:24 PM
 Platinum Member Join Date: May 2001 Posts: 2,369
Re: Up & Down hill shooting?

One of my favorite topic [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img]

There are at a minimum three common methods to resolve the uphill/downhill trajectory problem(s).

Here's a link to a recent article on this subject.
http://www.exteriorballistics.com/eb.../article1.html

For me it boils down to two distinct issues... does the shooter have the option to fire a round and then correct for a second round hit. If there is no option for a second round hit then an indepth understanding is probably desired.

Just to give a little hint of the "unseen" problems... What is your rifles' zero range? Is this the range you correct for the angled/inclined fire from? In other words...the target it 500 line-if-sight yards at 45 degrees (just to make it easy) 500 * .707 (the cosine of 45) = 353 yards... standard come-up fro 353 yards is about 5.5 MOA for a 308 vice the 10.5 or so 500 yard come-up... 5 MOA diff or a miss high by about 17.5 inches. WHAT about the 3.5 to 3.75 MOA of elevation already in the system to zero the rifle at 100 yards...we don't correct this value and it is important. To see how large this error could be we only need to think about a shot straight up or straight down. Zero the rifle at 100 yards (scope set to -0-). Find a tall cliff (El Capitan or some such) and shoot straight down....where will the bullet hit? It'll hit away from our point of aim in the 12 o'clock direction (relative to the rifle at time of firing the round) by the amount of correction required for the 100 yard zero (3.5 MOA for a 308 type rifle)...that little bit (3.5 MOA) can cause a fair miss at based on long range and big angles or big angles and small targets.

Sorry... told you this was a favorite of mine.

[ 09-18-2003: Message edited by: Dave King ]
#7
09-22-2003, 01:08 PM
 Silver Member Join Date: Apr 2003 Location: Newburgh NY Posts: 235
Re: Up & Down hill shooting?

Holy Hypotenuse Batman!!! You mean all those torture sessions they called geometry,trigonometry, and calculus they put me through are actually useful!!! I just hope I don't start having theorem flashbacks!
You could tell I was trying to forget my education by the spelling in some of my previous posts.

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