Adjusting for steep uphill/downhill shots

[DonVathome]

I know about how gravity affects your bullet and how the angle you shoot at also affects the flight (drop) of your bullet. Basically the bullet only drops due to gravity because of how far the bullet travels horizontally (parallel with the earth). I read an article a while back that said these was more to it than that but I cannot find the article and I do not remember what it said.

My question is this. I keep hearing stories about guys shooting over game because of steep angle shots. If you rifle is sighted in, say, 2? high at 100 yards, and hits 3? low at 300 then it seems to me that as long as the animal is up to 300 yards you should just hold dead on no matter what the angle, if this is true why do so many guys miss high? In my example if you range an animal at 300 yards but it is steep uphill/downhill all you need to do is still aim dead on right?

From what I remember the article I read said there was more to it and your bullet would hit high (in my scenario) and explained why. I think the article might have been in Huntin Fool.

Let's hear some answers from those who really understand the math and ballistics.

I read many stories about first shots being high from guys who know their guns, so I am trying to learn to save myself from missing a once in a lifetime shot.

 

[nochawk]

you have to shoot it for what the horizontal distance is from you. hold low

if you are shooting down hill at say a 45degree hill the range finder may say it is 200 yards away, but it may only be 50 yards in actual horizontal distance.

think of it as if you were in a tree stand looking down at a deer..from your stand to the deer may be 30 yards, but from the base of the tree the deer is only 10 yards away, so you would shoot it for 10 yards not 30.

also at an angle the body depth is smaller..it may be 30in from top to bottom but it may only be 15 side to side. the steeper the angle the less target area you get.

 

[stinkystomper]

gravity pulls at 9.8 M/S squared. Just ignore the squared part and look at the bullets flight time. In short, if the angle is more than 45 degrees past 200 yards you better think about putting it on the belly line. Don't worry about bullet speed, weight, etc. Weight, is weight, or as a flight test engineer, mass is mass. Gravity nevef r changes. Gravity is less at higher altitudes, but the variance is not enough to worry about. Just know how long it takes your bullet to arrive. Realize that every second your bullet is in the air its vertical velocity increases by 9.8 m/s. Dierction makes no determination on where to aim. The bullets velocity in the vector plane has two components. One component in the horizontal plane and one in the vertical plane. If you shoot downhill the bullets perceived path towards the animal is helped by gravity therefore the drop will be less. If you shoot uphill then the bullets velocity toward the target will be hindered by gravity resulting in a very small change in your bullets expected velocity. Instead of shooting uphill at 3600 fps you will probably be at 3591 or so. However the vertical component of gravity now will be significantly less. Again, aim low. This is the place most hunters don't understand. However, know flight time and multiply it by 9.8 meters. It is that simple, roughly. Don't add in coeficients of friction due to air, terminal velocity, subsonic aerodynamics versus sonic and supersonic. Were not talking about the F22 raptor, were talking about close being good enough. And yes, for any other engineers reading this 9.8 m/s IS good enough for hunting, don't over analyze things. Most people do that when trying to make others think their smart. I've used this several times and always hit my target. Just remember that usually anything less than 40 or 45 degrees in usually a normal shot for a rifle. The length of your fist held straight out in front of you is 10 degrees roughly. Hope this helps

 

[DonVathome]

So again, bottom line is if your rifle hits the way I described (2" high at 100 yards and 3" low at 300) hold dead on out to 300 no matter what the angle and you will get your animal - longer and then you need to start worrying about holdover, but I can never see why some have to hold under the animal, unless you have your rifle zeroed in for 300 yards or some long range like that.

 

[Ropinfool]

You need a calcuator and protractor as part of your hunting gear......lol.

 

[stevenclark]

if you look on the internet for things called cut charts, they show what your bullet/ arrows do at different angles. there is alot more affect on an arrow than a bullet from what i have learned.

 

[deserteagle500]

DONVATHOME,

you are right, and you are wrong. depending on the angle you may miss or you may hit. just go shoot a ray gun and you don't have to worry about it.




the only eagle with enough power and speed to kill and gut you with one shot

 

[gb22]

Donvathome,

You are right. Pretty much what's been said is right. The problem is, the angle is the EXCUSE often used when someone misses. If the animal is only 250 horizontal yards, but 600 total yards, you can still aim at it and the rule of 3s (3 inches high & never more than 3 low or 3 high out to 300) will still keep you from missing.

HOWEVER, wind, wiggle, jerking the trigger....there are still plenty of ways to miss. It wasn't my fault...never is....the angle got me is USUALLY the real reason someone misses.

 

[yukonjacko]

This is an article that explains it pretty well it seems.

http://www.wildsheep.org/magazines/article_uphill_shooting.htm

 

[NMPaul]

This is a great question and you asked it the right way.

If you gun is set2-3" high at 100 and only 3" low @ 300 yds hold dead on.

I agree with you on that.

Extreme angle shots give you a slightly smaller target and few of us practice them. Like someone else said. Blaming the angle takes some heat off.

I guess the math really counts when you start to get 400+ yds out there. But then again, those are not typically all that severe of an angle.

 

[DonVathome]

I was WRONG!

Yukonjako that is EXACTLY what I read and forgot - thanks for the link.

Here is some info from the link:

"To understand uphill/downhill shooting, you must first understand that your line of sight and barrel are not parallel. If you are like most rifle hunters, you sight your gun in to shoot several inches high at 100 yards. To accomplish this, your barrel must point higher than your scope?s line of sight. As the distance increases, your barrel will point proportionally higher and higher."

"Using the bullet and load table at the bottom of the page as an example, to achieve a 300-yard zero, the barrel must point almost 18? high at 300 yards. Why? Because at 300 yards, gravity is going to push the bullet down about 18?. Thus, you will be zeroed at that distance. At 500 yards, the barrel actually points about 31" higher than the line of sight."

"By now you might be thinking, "Ok, so at 500 yards at a 60-degree angle, my bullet is affected by gravity just the same as 250 yards on flat ground, so I would aim like it was a level 250 yard shot, right?" WRONG! This is the a myth in uphill/downhill shooting. The reason is very simple. Forget about gravity for a moment, remember, you are actually shooting at 500 yards and your barrel is pointed much higher from your line of sight at 500 yards than 250 yards."

This is what I remember reading a long time ago, this is very good info that I bet 99% of hunters do not know and lets a lot of game escape.

Thanks again yukon, exactly what I was looking for.

 

[NMPaul]

Is it safe to say that the uphill shot is impacted more than the downhill?

 

[DonVathome]

I do not think so but I am not sure!!!!!!!!!!!

 

[Bambistew]

Can I use 32.2 fp/s^2 instead of 9.8m/s^2?

 

[toughshed]

Uphill, downhill, all the same...the shot is "shorter" than what your rangefinder says because gravity acts on the horizontal distance, not the flight path distance...so if you were shooting at an elk up OR down a 45 degree slope that is 200 yards away, gravity only affects the bullet over the horizontal distance of 141 yards...so yes, for shots in the normal range of a high powered rifle, it really doesn't matter, elk still dies. But for longer range shots up or downhill it matters, especially when the slope is steep.