Why is it so

[ctshooter]

Want to add one bit of science to the conversation. I'll start by saying I have no experience shooting up or down hills - so this is all very interesting and quite a bit of learning. Thank you all who are contributing. 

I've read a few times in the posts the when shooting up hill the effect of gravity is lessened. The effect of gravity is a constant of 32 feet / sec x sec and will never change. When you shoot uphill, and let's stick with the simple 45 degree angle, the energy of the pellet is split across the x and y axis. Half of the energy is pushing the energy along the horizontal x axis and half of the energy is pushing along the y axis. It is the energy in the y-axis that is acting against the force of gravity pulling the pellet down. 

Where I start to get confused is trying to take the science, add in what is seen in the field, and explain it accurately with math. 

 

[Guest]

Well the gravitational force on the pellet is the same constant whether it is horizontal or vertical (I suppose there is a small imperceptible difference going vertical above the starting point of reference/plane. However that wouldn’t be measurable by a layman. I think the holdover wouldn’t be the same at a steep angle because the gravitational force/wind have a mitigated impact on the trajectory’s horizontal drag. At say, 70% Angle, you would significantly less horizontal drag but you would still have some, and obviously you are substituting horizontal with the vertical impact of gravity and wind/humidity. I think the main thing is the flight pattern is different because of this reduced horizontal drag from your initial frame of reference. The way you should be able to see this is shooting at the same tree rather than the two trees, since you said one is further than the other.


I think Stoti’s reference to the flatter trajectory is the picture one should imagine. Instead of an asymmetrical parabola, the steeper the angle the more symmetrical that parabola is. You will still have the same drag forces in place and effecting the projectile, though the parabola shape of the flight pattern has been altered based on you initial starting frame+angle.

Maybe that doesn’t make sense but between breakfast and diapers that is the best your getting from this guy. That drawing is from “The Naked and the Dead” by Norman Mailer. Random, I know, but I grabbed it since I knew the drawing well. Your horizontal flight drag is getting increasing amounts of vertical flight drag. This reduces the need for vertical holdover on your scope.


The holdover that will be used still is obviously the x axis plane with wind on different heights of y axis is causing the the projectile to move horizontally on its flight along y axis (in a 3D rendering you could see this clearly); imagine shooting perfectly straight on the y axis and you would see the pellet go to one side or the other of the y axis, maybe both sides with crosswinds). 


Okay back to the family.

 

[bandg]

And to complicate the topic further, it is a bit different if shooting upwards vs downwards. Both will require less holdover than one expects at near ranges but they will be slightly different. And at extreme ranges, shooting downhill will require progressively less holdover than will shooting uphill while shooting uphill will require progressively more holdover than will shooting downhill. Any variation of aim above or below horizontal at near (airgun) ranges will require less holdover. 

It was stated above that gravity works with the same constant on the pellet. While it is true that gravity doesn't change, the PATH OF THE PELLET (up or down) in relation to the vector of gravity (always the same) produces different EFFECTS on the pellet dependent on its path. Gravity effect (amount of drop) is highest at horizontal shooting and lessens as the path of the pellet goes above or below horizontal.

 

[Windmill01]

Thank you to all who contributed. I will go out today and do some pruning

Gary

 

[ctshooter]

badng - the uphill/downhill thing is what still confuses me. I get the uphill as you have upward force on the pellet countering the effect of gravity. But when you shoot downhill the pellet has downward force the is acting in the same direction that gravity is - so how to you end up holding over and not under. Really trying to get my head around the downhill.

 

[Guest]

badng - the uphill/downhill thing is what still confuses me. I get the uphill as you have upward force on the pellet countering the effect of gravity. But when you shoot downhill the pellet has downward force the is acting in the same direction that gravity is - so how to you end up holding over and not under. Really trying to get my head around the downhill.

Because you are not shooting perfectly straight down the y axis but rather a degree horizontally along some form of a triangle like an asymmetrical parabola. Your holdover is less than it would be shooting a trajectory along the x axis, but there is still the gravitational force at play. It makes your holdover placement as though the object is closer to you. If you look at my other post above with the drawing of the asymmetrical parabola, imagine if they were tilted on an 45 degree angle down; in such an example you can imagine your point of impact being somewhere in the middle of that curve before gravity has its way.

 

[ctshooter]

I think I'm getting it, thanks. You can't just think of the flight path of the pellet, but the whole system including the line of sight, the angle of barrel in relation to the line of sight, the parabolic path of the pellet being altered by the y-axis forces (either up or down) on the pellet. 

 

[bandg]

I think I'm getting it, thanks. You can't just think of the flight path of the pellet, but the whole system including the line of sight, the angle of barrel in relation to the line of sight, the parabolic path of the pellet being altered by the y-axis forces (either up or down) on the pellet.

I would say yes, but to understand the arc of the projectile you don't really need to consider line of sight relation to bore. The projectile knows nothing about line of sight but it still will travel in an arc the shape of which is determined by velocity, weight, and inclination.

Maybe think of it like this-if you shoot a pellet off the edge of the grand canyon you could hit the river below. Gravity pulls the pellet down but it started on a downward angle so it follows a relatively more "straight" path downward with gravity curving it downward relatively less. And in that case gravity wouldn't be "slowing it" much at all, if any. More like the left arc of the 4 drawn above. But then if you stand at the river below and shoot upward toward the cliff edge the pellet would be slowed (moving more against gravity) and ultimately curved relatively more by gravity. It would never be able to reach the cliff above, not enough energy present to overcome the gravity. More like the bottom arc of the 4 above.

 

[Guest]

I think I'm getting it, thanks. You can't just think of the flight path of the pellet, but the whole system including the line of sight, the angle of barrel in relation to the line of sight, the parabolic path of the pellet being altered by the y-axis forces (either up or down) on the pellet.

Yeah you got it. It’s more simple when you stand back and just look at the shapes, but when you are overthinking you can definitely mess with your mind on a quick draw. Wind, for example, has not been mitigated on a downhill shot.

 

[ctshooter]

Wind, for example, has not been mitigated on a downhill shot.

Right - and I think I understand shooting uphill, if you are too close to the ground, your pellet could be effected by updrafts too.

 

[Guest]

Wind, for example, has not been mitigated on a downhill shot.

Right - and I think I understand shooting uphill, if you are too close to the ground, your pellet could be effected by updrafts too.

When I used to do 1000 yard plus shots with powder burning rifles in the .30 cal range I would often shoot across a few hills/valleys and you could see the bullet in slomo moving up and then down a good 2-3 times with the heat and wind making pockets of colder/hotter/still air/windy. Crazy, but it was some of the most entertaining shooting you could do. You would have to take 3-7 shots just to land your target.

 

[dan_house]

Matt Dubber says this



https://youtu.be/Zf6d-6A-9Uk

 

[bandg]

And he certainly seems to shoot a lot. I would bet his info is correct. I don't use any "programs" for my shooting so I most certainly can't speak to the math on this but the important point seems to be that at extreme angles the drop seen is actually less than most will estimate (thus impacting high or missing high). As a young man I was able to shoot from elevated banks into rivers and from river banks to treetops on elevated banks a lot. My past (though long ago) experience aligns with Dubber's view and I believe it is even more noticeble when shooting downward than when shooting upward, expecially as range lengthens. JMO, of course.