Horizontal distance argument

[bosulli]

I get into the is argument all the time, and with engineers and technical writers for integrated circuit companies. How do I explain to someone that thinks they now everything, that it does not matter if you are aiming up or down at a target that you have to aim lower? I tell them that that its the horizontal distance that effects the bullet drop not if you are aiming up or down. There must a "trajectory for dummies" somewhere that I can show them.

 

[Graham]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bosulli</div><div class="ubbcode-body">How do I explain to someone that thinks they now everything...</div></div>There's your problem.

Try the Sierra reloading manual.
http://www.exteriorballistics.com/ebexplained/article1.html

 

[bosulli]

Re: Horizontal distance argument

Thanks, that is excellent. I am going print that to a PDF and save Iphone, for next time.

 

[RFtinkerer]

Re: Horizontal distance argument

As an electrical engineer for a consumer electronics company (who fortunately fully realizes he don't know nothin), I would respond to breaking the distance into its horizontal and vertical components. Apply gravitional drop to the horizontal component only. Standard HS physics.

 

[john_1182]

Re: Horizontal distance argument

i have shown people buy laying a ruler on a table and then raising the ruler up to say 45 deg, and marking where the end of the ruler is then doing the same for a 80 deg rise, they soon see how the angle effects horizontal distance.

 

[J-ROD]

Re: Horizontal distance argument

Ask them if you were shooting straight up/down at 1,000yds (neglecting wind, spin drift and earth's rotation) how "high" would you have to aim.

 

[threetrees]

Re: Horizontal distance argument

if they think they know everything, they have not reached the 'actually, i know nothing' level yet.

 

[flounderv2]

Re: Horizontal distance argument

If they are engineers, simply show them the pythagorean theorem and Pythagorean trigonometric identity and draw it from a shooters viewpoint.


http://en.wikipedia.org/wiki/Pythagorean_theorem
http://en.wikipedia.org/wiki/Pythagorean_trigonometric_identity

Simply put.
Bullet flight from point A-B is s measure of distance.
Actual distance can be calculated using the above theorems.
Bullet drop is an result of gravity's affect over a period of time (i.e the time the bullet is in the air)
Time is distance/velocity or t=d\v

Also, I find that the question of shooting straight up/down always helps put things into perspective.

If they dont understand that, then fire them because they are piss poor engineers.

 

[milo 2.0]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RICE ETR</div><div class="ubbcode-body">Ask them if you were shooting straight up/down at 1,000yds (neglecting wind, spin drift and earth's rotation) how "high" would you have to aim. </div></div>

I'll bite, what's the answer?
To me, you'd have to hold low, because even with iron sights you can't have a point blank zero.
Milo

 

[J-ROD]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: milo-2</div><div class="ubbcode-body">
I'll bite, what's the answer?
To me, you'd have to hold low, because even with iron sights you can't have a point blank zero.
Milo </div></div>


The line of sight of scope/irons would almost be parallel with the bullet's path (not 25-40moa up as in a typical horizontal 1K yd shot)...the difference would be the slight angle due to scope or iron sight height. If you get real technical, I guess you would have to factor in the very very slight factor of gravity in the x direction due to the tiny angle mentioned above. Nonetheless it's just the angle thing taken to the extreme to show that the angle of the shot does change the dope.

 

[milo 2.0]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RICE ETR</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: milo-2</div><div class="ubbcode-body">
I'll bite, what's the answer?
To me, you'd have to hold low, because even with iron sights you can't have a point blank zero.
Milo </div></div>


The line of sight of scope/irons would almost be parallel with the bullet's path (not 25-40moa up as in a typical horizontal 1K yd shot)...the difference would be the slight angle due to scope or iron sight height. If you get real technical, I guess you would have to factor in the very very slight factor of gravity in the x direction due to the tiny angle mentioned above. Nonetheless it's just the angle thing taken to the extreme to show that the angle of the shot does change the dope. </div></div>

Most of us run 20MOA bases, I have two with 40MOA. That's gotta factor in.

 

[J-ROD]

Re: Horizontal distance argument

It's all relative. My only point is that the effects of gravity are greatest when shooting horizontal and the least (basically zero) when shooting vertical therefore angles do lessen your elevation adjustment.

 

[Lowlight]

Re: Horizontal distance argument

A simple drawing I did for a lesson

All three lines are of equal distance

 

[Arbiter]

Re: Horizontal distance argument

Now your MS Paint drawing has me all confused, Frank.

The best way to describe it I've found to be using the hypothetical vertical shot. Ignoring the scope offset and pre-existing scope zero, anyone will be able to tell you that their vertical shot would produce a perfectly straight trajectory without any apparent "drop". Then you work them backwards to a more realistic angle and explain that the effective distance is a function of the angle and the measured distance...they'll get it eventually.

 

[J-ROD]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Arbiter</div><div class="ubbcode-body">Now your MS Paint drawing has me all confused, Frank.

The best way to describe it I've found to be using the hypothetical vertical shot. Ignoring the scope offset and pre-existing scope zero, anyone will be able to tell you that their vertical shot would produce a perfectly straight trajectory without any apparent "drop". Then you work them backwards to a more realistic angle and explain that the effective distance is a function of the angle and the measured distance...they'll get it eventually. </div></div>

Lol...yes!

 

[rpk762]

Re: Horizontal distance argument

Lol I always laugh at these questions. I just tell them just range it then do some math then there is no guessing.

The true answer is how far is your scope sighted in for? Got a 100yd zero and the critter is 600yds away from you (level distance) you better not be just aiming low. You better be playing with your scope knobs.

 

[Lowlight]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Arbiter</div><div class="ubbcode-body">Now your MS Paint drawing has me all confused, Frank.

The best way to describe it I've found to be using the hypothetical vertical shot. Ignoring the scope offset and pre-existing scope zero, anyone will be able to tell you that their vertical shot would produce a perfectly straight trajectory without any apparent "drop". Then you work them backwards to a more realistic angle and explain that the effective distance is a function of the angle and the measured distance...they'll get it eventually.</div></div>

Not really the change in trajectory from straight line to an angle is the effect of gravity on the bullet. There are some small changes from other effects as Sierra notes, but for this simplified demonstration, the bullet is only be effected by gravity across the straight line distance.

This is where the original "rifleman's rule" derived its data... the effects of gravity, even though all three lines are of equal distance is only being effected part of the way on a straight line chart like above.

So you figure, if you have a 1000 yard shot on an angle, you only use your dope across the distance effected, for example 880 yards...

<span style="font-style: italic">The Rifleman's Rule (RR) Method derived by these analyses is the following:
Measure the inclination angle of the target above or below the horizontal direction.

Measure the slant range distance to the target.
Multiply the slant range distance by the trigonometric cosine of the inclination angle (this gives the horizontal projection of the slant range).
Use the Bullet Path (or come-up or come-down) from the level trajectory at this horizontal projection distance to adjust the aim for the inclined target.

In other words, pretend that the inclined target is at a horizontal distance equal to the slant range distance multiplied by the cosine of the inclination angle, and aim as if the target were really at that horizontal position. </span>

It's not confusing at all, it's gravity, which is why there are slightly different values for uphill versus down hill.

 

[tnichols]

Re: Horizontal distance argument

Man am I glad I just shoot for fun...all this reading and thinking makes my brain hurt!

 

[Sterling Shooter]

Re: Horizontal distance argument

I think Frank confused some folks with the statement "all lines are of equal distance". The slant line to target is greater length than the horitontal line to target. Gravity is related to horizontal distance, which always being shorter than slant means always holding low, whether shooting up or down hill.

 

[Sterling Shooter]

Re: Horizontal distance argument

I think Frank confused some folks with the statement "all lines are of equal distance". The slant line to target is greater length than the horitontal line to target. Gravity is related to horizontal distance, which always being shorter than slant means always holding low, whether shooting up or down hill. In illustration, the blue line to target is about 7/8ths length of the black line to target.

 

[Lowlight]

Re: Horizontal distance argument

Technically they are all the same distance. If you laser range find a target across the horizontal distance, say 1000 yards, and then you laser a target up or down the same 1000 yards, the straight line distance to target is the same, but the angle changes the effect of gravity.

So if all three distances are 1000 yards, the horizontal distance is effected across 100% of that, the angle distanced are effected by gravity less so the dope necessary to hit the angles will be less. (the 7/8ths as noted)

I can see where the confusion would come in, and yes you are correct in your description of it SS... but the lines are of equal distance as measured, just not equal effect.

 

[Panhandle]

Re: Horizontal distance argument

If you really want to play with your friends minds explain to them how when your are shooting uphill the air is becomming less dense and when you are shooting downhill the air is become more dense which has different effects on the bullet (negligible i know).

Also, when your shooting down hill gravity is helping your bullet a little as opposed to working against your bullet some when your shooting uphill. Probably not all that significant and the riflemens rule will get you in the ball park.

 

[Arbiter]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Arbiter</div><div class="ubbcode-body">Now your MS Paint drawing has me all confused, Frank.

The best way to describe it I've found to be using the hypothetical vertical shot. Ignoring the scope offset and pre-existing scope zero, anyone will be able to tell you that their vertical shot would produce a perfectly straight trajectory without any apparent "drop". Then you work them backwards to a more realistic angle and explain that the effective distance is a function of the angle and the measured distance...they'll get it eventually.</div></div>

Not really the change in trajectory from straight line to an angle is the effect of gravity on the bullet. There are some small changes from other effects as Sierra notes, but for this simplified demonstration, the bullet is only be effected by gravity across the straight line distance.

This is where the original "rifleman's rule" derived its data... the effects of gravity, even though all three lines are of equal distance is only being effected part of the way on a straight line chart like above.

So you figure, if you have a 1000 yard shot on an angle, you only use your dope across the distance effected, for example 880 yards...

<span style="font-style: italic">The Rifleman's Rule (RR) Method derived by these analyses is the following:
Measure the inclination angle of the target above or below the horizontal direction.

Measure the slant range distance to the target.
Multiply the slant range distance by the trigonometric cosine of the inclination angle (this gives the horizontal projection of the slant range).
Use the Bullet Path (or come-up or come-down) from the level trajectory at this horizontal projection distance to adjust the aim for the inclined target.

In other words, pretend that the inclined target is at a horizontal distance equal to the slant range distance multiplied by the cosine of the inclination angle, and aim as if the target were really at that horizontal position. </span>

It's not confusing at all, it's gravity, which is why there are slightly different values for uphill versus down hill. </div></div>

All of that is precisely correct, but your sentence "the effective distance is a function of the angle and the measured distance" most succintly describes the important factor in play. Once someone understands that the true horizontal distance is what matters, the rest becomes easy.

 

[Sterling Shooter]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Technically they are all the same distance. If you laser range find a target across the horizontal distance, say 1000 yards, and then you laser a target up or down the same 1000 yards, the straight line distance to target is the same, but the angle changes the effect of gravity.

So if all three distances are 1000 yards, the horizontal distance is effected across 100% of that, the angle distanced are effected by gravity less so the dope necessary to hit the angles will be less. (the 7/8ths as noted)

I can see where the confusion would come in, and yes you are correct in your description of it SS... but the lines are of equal distance as measured, just not equal effect. </div></div>

I think we're on the same page. For any uphill or downhill target the horitontal distance to such target will always be shorter. Yes?

 

[Early Cuyler]

Re: Horizontal distance argument

Well I just had a palm-to-forehead moment... I read this thread, read the linked article, looked at ballistics calculators, and I just wasn't getting it. I was thinking "well the bullet flight time will be the same so the effect of gravity will be the same." Which is correct. Then I thought, "well if the drop is the same, the POA/POI should be the same." Which was waaaaaay wrong.

The bullet drop is the same as the reduction in horizontal distance is proportional to the reduction in horizontal muzzle velocity. This means same time and same drop. My assumption was that the drop was from POA rather than bore line. When I finally put 2 and 2 together I figured it out.

As always: Thanks

 

[MitchAlsup]

Re: Horizontal distance argument

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bosulli</div><div class="ubbcode-body">There must a "trajectory for dummies" somewhere that I can show them. </div></div>

Trajectory for dummies:

A) bullets drop
B) when the PoA is up or down a cosine of the shot-angle takes place.
C) Cosines of small angles are always less than 1.0
D) Thus bullets shot up or down drop less than bullets shot horizontally.

 

[Mr.Maim]

Re: Horizontal distance argument

Wow! Great topic! Thanks for the drawing Lowlight, that nailed it for me, a visual learner.

I have SOOOOO much to learn!