Shooting up

[George]

If you are asking me to do the math for you, 1) I must politely decline for now on the grounds I have other more pressing demands on my time and 2) I only brought up the theory (having missed its introduction to the thread earlier) as a suggestion without making any claim as to its usefulness, so while I too am interested it figuring out its validity I'm not obligated to prove anything.

I can do my own math, but thanks for the thought.

As I said above, what I'm looking for is the idea behind the "calculate drop based on the spot below the target theory," you mentioned. I'm interested to find out what adherents to the theory claim are the mechanism, the physics, behind the idea. I was hoping you would describe that in explaining your idea for testing it. Without being obliged to do so, of course. I'll keep looking. Somebody out there has to know, the idea has been around for at least three decades.

Spence

 

[Claude Mathis]

I aim at my target, the angle should make no difference - gravity is a constant regardless of your initial angle and will attract the ball in the same way.

Gravity effects the trajectory less shooting up or down. How much it effects it depends on the angle.

Since your sights are set to compensate for bullet drop, and there is less bullet drop when shooting at an up or down angle, you must hold lower than normal to maintain the desired point of impact.

It is gravity working on the bullet during its flight time that causes it to drop. If you were to shoot straight down, the bullet would have no curved trajectory, it would travel toward the earth in a straight line, just as if you simply dropped it. Likewise, if you shoot straight up, the bullet travels up in a straight line until its momentum is expended. Again, there is no curved trajectory.

 

[bender20]

Talked to my grandpa who told me about the idea of just use the straight line distance. He told me that he was told that it was only useful for either short ranges i.e archery from a tree or out to about 200 yards under “reasonable angles” and he always understood it as an estimate to get you close enough for hunting accuracy and as far as he understood it was by no means gospel. I on the other hand either misunderstood his original explanation or overtime distorted what I remembered and understood it as truth until Spence showed me the error of my ways. So it may be a case of originally it was close enough and over the years got distorted into gospel and people being people came up with a myriad of reasons as to why it was true.

 

[Elnathan]

My ideas are pretty hazy, but I'll take a stab at explaining why I think it might work:

The angle at which force of gravity interacts with the line of departure, and thus the proportion of gravitational force which acts on the bullet perpendicular to the line of departure (i.e., the drop as perceived by the shooter, not the true drop as defined by Lyman) is in direct proportion to the angle of the line of departure from horizontal. In the same way, the ratio between the length of the hypotenuse (bullet path) and the length of the ground leg (the distance to the spot directly beneath the target) is also directly tied to the angle of elevation.

Thus, two ratios defined by the same variable - logically, it should be possible to define the ratio between the two ratios. The leap is assuming that the ratio is 1:1; i.e, that as the angle increases, the increasing discrepancy in length between the actual path of the bullet and and the ground distance is exactly compensated for by the decreasing effect of gravity in a perpendicular direction to the line of departure.

My gut instinct is that it does work - after all, if you were to loose off a ball straight up (in an ideal world with wind or imperfect balls or whatnot) the ball would not deviate from the path of departure at all, since the force of gravity would be 100% in line with the line of departure. It would go straight up and straight back down the muzzle like something out of Looney Toons. Effectively, the ball would interact with the sights in terms of drop in exactly the same way that it would if fired with the muzzle touching the target - zero drop. That is pretty suggestive, but I don't know how to prove it mathematically, and in something this complex it is easy possible that I am overlooking a critical variable.

 

[bender20]

If you aimed straight up or down your bullet would not travel straight up or down. Your sights sit higher than your bore. But furthermore your not comparing apples to apples. Straight up and straight down take out the effects of gravity on the projectile interms of drop. All that proves is that you must hold low when the target is both beneath your feet or above them. The key is the angle at which gravity is effecting your projectile and how that changes the parabolic motion of the projectile in relation to how your sights where set when you sighted in while shooting flat.

 

[bender20]

Not sure if this exactly answers your question Spence but found this an interesting read. Towards the bottom is the info I’m referring to but a good read in its entirety.
http://www.millettsights.com/resources/shooting-tips/mathematics-for-precision-shooters/


Upon further investigation it looks like you multiply the cosine of the angle by the actual distance to target and this will give you the range that you should set up your shot for.

Example:
Your range finder says 230 yards. The cosine of a 15-degree angle is .9659 times 230 equals 222.1629 yards, you will have to adjust your scope or hold 8 yards lower at 222 yards.

 

[Elnathan]

If you aimed straight up or down your bullet would not travel straight up or down. Your sights sit higher than your bore.

If, however, I aimed the bore straight up and down, the bullet would go straight up and straight back down. Ignoring non-gravitational forces, of course.

Straight up and straight down take out the effects of gravity on the projectile interms of drop.

Yeah, that was kind of the point. The amount of bullet drop below line of departure at 90 degree elevation (zero ground distance to target) is the same as the bullet drop with zero distance to target on the horizontal plane - zero. So I can hold the sights in the exact same relationship to the target shooting any number of yards straight up as I do shooting at o yards horizontally. Interesting how it works out, isn't it?

All that proves is that you must hold low when the target is both beneath your feet or above them. The key is the angle at which gravity is effecting your projectile and how that changes the parabolic motion of the projectile in relation to how your sights where set when you sighted in while shooting flat.

Yes, I believe I've touched on that phenomenon...

 

[bender20]

I apologize the cosine formula is the exact same as estimating the flat line distance. brain fart. So far no info on an actual formula but I have found the cheaper rangefinders with compensation built in use this formula for their calculations

 

[Claude Mathis]

It's this simple. :wink:

GRAVITY...

 

[Skychief]

It's this simple. :wink:

GRAVITY...

:haha:

 

[Grumpa]

Been trying to read through all this without getting a headache.


the simple fact is that at the distances we shoot with muzzleloaders, none of this matters. The wobble factor for any shooter is going to be greater than the effect of gravity being discussed here. Start trying to factor this into your aiming, and someone else will be tagging that deer. :grin:

Now I'm going to relax, and search for a thread on which side of the patch should face the ball, or what's the best patch lube, or should we wrap the flint in leather or lead....

Richard/Grumpa

 

[azmntman]

:hmm: ...........well I once saw a nice 4pt buck about 3o' up a huge cedar (12A unit in far N AZ). But he had done been eaten by a VERY strong Mnt Lion so I didn't shoot at him. Sure wish I could find a few of the photos (before digital) that would back up some on my wild tales! This one is true blue though!