Calculating zero distance elevation

Yama Arashi

Yama Arashi

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Jun 9, 2011
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#1
Is there a way to calculate zero come up with a ballistics calculator, without specifying an actual zero distance?

Ex: Red dot or LPVO, 1/10th MIL clicks, 2.63 height over bore, 0 cant on rail or mount, 150gr at 2700fps

Trying to determine what the come up would/should be at specific distances short of 100 (25, 36, 50) without specifying an actual zero distance in the calculator, but they require a number input for that field.
 
#6
To ask more succinctly, what would my come-up be at 36yds for example, with the given inputs?

I'm toying with capped elevation LPVO's and 'combat zeros', as opposed to a standard 100yd zero, and trying to determine elevation come up in MILs, but the ballistic calculators require a number above 0 to be entered in the zero distance field, which throws everything off.

Specific examples are a - Kahles K16i, 0 cant on rail or mount, 2.7 height over bore, 55gr at 3050fps
- ATACR 1-8, 0 cant on rail or mount, 2.63 height over bore, 150gr at 2700fps

Briefly messed with them at the range last night, and the NF required 4.6 MILs to be on at 36. The Kahles required 3.3 MILs

I suppose that may bring into the equation how/if the scopes were centered/zeroed from the factories.

Obsessing basically..........
 
#8
They've been shot. Just trying to figure out the math, and see if the numbers jive, etc.

Trying to determine if it's possible to calculate without entering an actual zero distance in a ballistics calculator, as long as all other known parameters are entered. The calculators don't seem to like that.
 
#9
Yama Arashi said:
Is there a way to calculate zero come up with a ballistics calculator, without specifying an actual zero distance?

Ex: Red dot or LPVO, 1/10th MIL clicks, 2.63 height over bore, 0 cant on rail or mount, 150gr at 2700fps

Trying to determine what the come up would/should be at specific distances short of 100 (25, 36, 50) without specifying an actual zero distance in the calculator, but they require a number input for that field.
Click to expand...
To determine any come up (drop) then you must have a starting point (zero).

If your bullet crosses the line of sight ever, then it is zero'd for some distance. If you use any ballistic calculator, you can input your specs and match them to your actual drop by playing with the zero distance until they match.

Once the zero distance is found, you can determine come ups for any other distance from there.
 
#11
A 36yd zero is no more or less nonsensical than a 25 or 50yd zero for the intended rifle/optic use and a 'combat zero', with an elevation turret that is capped and won't be dialed. I have other rifles/optics better suited and intended for precision and dialing.

Simply a curiosity of whether or not come-up from the bore, in conjunction with the optic height, could be calculated using all other available parameters, and seeing if it jived with my aforementioned results. Wanting to understand and be able to calculate the math of such basically; trajectory and holds after zeroing aren't in question.

It doesn't seem as if any ballistic calculators are able to estimate such from the muzzle (0 distance for the 'zero range' input field) without getting all sorts of skewed results.

Scott from Vortex commented elsewhere that he has had to dial 7 MILs with a 2.5" height over bore at 8yds, so my results don't seem to be out of the norm. I'm sure factory zero settings at the erector vary with model/manufacturer, etc., but I wasn't expecting to need that much come up to zero at the aforementioned distances.

Thank you everyone for the replies.
 
#14
I think all my explaining is making the actual question more complicated than it is. :LOL:

I'm not questioning what a particular zero range will accomplish, if it can be achieved, or what the trajectories/holds etc., will be after setting zero.

More along the lines of, can a ballistics calculator tell you what elevation will be required to achieve a particular zero? (In the same way it can tell you what the required elevation will be for a particular distance *after* you've already input a set zero distance) It doesn't seem like they're designed or able to do so with the usual inputs. Or is there a mathematical formula/equation for being able to figure it out without actually shooting it?

Probably a question no one has bothered asking or needed to ask, for good reason. :rolleyes:

Using the Shooter app for example, which is the only one that will allow me to zet '0' as the zeroed range - zeroing the 7.62/150gr rifle/optic combination at 1yd would require 52.1 MILs of come up. Calculator says 36yds would require 2.2 MILs of come up, whereas it took me 4.6 MILs of come up to be zeroed at 36.

So *is* the calculator actually working correctly in this regard, and I needed more elevation to zero because of where the erector/reticle was factory set at 0 on the elevation turret in relation to all the other parameter inputs? Or is a ballistics calculator simply incapable of estimating what a zero distance will require in click elevation from the muzzle, in conjunction with the height over bore and bullet weight/velocity, without having a pre-established zero range?

Yes, I have, can, and will, just shoot the damn thing though............
 
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#15
I’m not an expert on ballistic programs. My unscientific answer is no, won’t work.
One reason that comes to mind is that the receivers, scopes and barrels are not that precisely made.
 
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#16
There won't be any come up. It will be come-downs out to the same height of your scope over the barrel if your scope is mounted in a normal position over the barrel. Unless you can side-mount the optic on the same level relative to the Earth as the barrel, and then you will have immediate come-ups.

Most rifles have come-downs at close range even when the rifle is zeroed @ 100, so I imagine it would just make your holds that much more severe because the parabola never rises above the rifle barrel relative to the earth.
 
#17
Fig said:
There won't be any come up. It will be come-downs out to the same height of your scope over the barrel if your scope is mounted in a normal position over the barrel. Unless you can side-mount the optic on the same level relative to the Earth as the barrel, and then you will have immediate come-ups.

Most rifles have come-downs at close range even when the rifle is zeroed @ 100, so I imagine it would just make your holds that much more severe because the parabola never rises above the rifle barrel relative to the earth.
Click to expand...

I'm sorry, but that's not true. Time to go back to external ballistics school.
 
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#19
Fig said:
Ok, explain.
Click to expand...

If you look at a typical plot of the bullets trajectory relative to the line of sight of the scope, for a rifle/scope sighted in at 100 yards, the bullet will leave the barrel at a slight upward angle, ( which is below the line of sight ), and end up at the line of sight around 100 yards. Then the bullet will continue to drop below the line of sight. Since the bullet is below the line of sight between the firing line and 100 yards you have to dial in a "come up" if you want the bullet to impact your aiming point which is closer than 100 yards.
 
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#21
Starting to branch off here, but as ShtrRdy stated, it does require 'come up' - which is rotating the elevation turret UP and moving the erector in relation to the barrel, so that the barrel, in relation to the reticle placement, is angled up to to make the bullet trajectory meet the reticle hold at a given distance. This is necessary, as in the aforementioned example, as the bore line is well below the optic height over bore, so it has to 'come up' to intersect.

And with a 100 yard zero, the bullet starts below the optic centerline and is traveling with an upward trajectory until it hits 100, where it stays flat for X number yards and then starts dropping again. Where it's rising or falling is completely contingent on the zero distance in relation to trajectory.
 
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#23
Fig said:
Ok, explain.
Click to expand...
ShtrRdy said:
If you look at a typical plot of the bullets trajectory relative to the line of sight of the scope, for a rifle/scope sighted in at 100 yards, the bullet will leave the barrel at a slight upward angle, ( which is below the line of sight ), and end up at the line of sight around 100 yards. Then the bullet will continue to drop below the line of sight. Since the bullet is below the line of sight between the firing line and 100 yards you have to dial in a "come up" if you want the bullet to impact your aiming point which is closer than 100 yards.
Click to expand...
What he is saying is that as you move the turrets for your come ups to extend your "2nd" zero further out. Your "first" zero (the bullets crossing the line of sight on the way up) simultaneously moves closer to the muzzle.

Therefore, assuming a standard 100 yard zero, all ranges are come ups.
 
#24
rth1800 said:
Ok, this just went over the line stupid. Checking out.
Click to expand...

I'm amazed any amount of civility on this forum is ever maintained.

Your post about a bullet continuing to rise past 100 yards when zeroed at 100 yards is completely erroneous (albeit contingent on height over bore and velocity) Any caliber example I actually own (5.56, 6.5, 7.62, 300, 338) with HOB measurements ranging from 1.99" to 2.7" is dropping past 100 when zeroed at 100.
 
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#25
Yama Arashi said:
I think all my explaining is making the actual question more complicated than it is. :LOL:

I'm not questioning what a particular zero range will accomplish, if it can be achieved, or what the trajectories/holds etc., will be after setting zero.

More along the lines of, can a ballistics calculator tell you what elevation will be required to achieve a particular zero? (In the same way it can tell you what the required elevation will be for a particular distance *after* you've already input a set zero distance) It doesn't seem like they're designed or able to do so with the usual inputs. Or is there a mathematical formula/equation for being able to figure it out without actually shooting it?

Probably a question no one has bothered asking or needed to ask, for good reason. :rolleyes:

Using the Shooter app for example, which is the only one that will allow me to zet '0' as the zeroed range - zeroing the 7.62/150gr rifle/optic combination at 1yd would require 52.1 MILs of come up. Calculator says 36yds would require 2.2 MILs of come up, whereas it took me 4.6 MILs of come up to be zeroed at 36.

So *is* the calculator actually working correctly in this regard, and I needed more elevation to zero because of where the erector/reticle was factory set at 0 on the elevation turret in relation to all the other parameter inputs? Or is a ballistics calculator simply incapable of estimating what a zero distance will require in click elevation from the muzzle, in conjunction with the height over bore and bullet weight/velocity, without having a pre-established zero range?

Yes, I have, can, and will, just shoot the damn thing though............
Click to expand...
I think what you are getting at is, "How can I find out what the actual drop is from a straight and level muzzle position".

Yes, you can do that. Set 1 yard as the zero point, and make the zero height the same "negative" value as your sight height. So set zero height as -2.3" as an example.
 
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#26
Is your question: “if I factory-zero a scope, and if I know the other rifle and bullet details, can I use software to know clicks from factory zero”, the answer is no, unless you get really lucky. As rth1800 said/implied, from the factory or your build bench all of this stuff isn’t going to line up perfectly. Even two sets of identical gear probably won’t end up with the same adjustment from factory zero.

But you likely can get a ‘good enough for battle zero’ without range time if you carefully boresight at a known distance, like 5 yards. Before you do that, enter all your details into the software, including the boresight distance as your zero, and adjust the Elevation Offset in your software (assuming yours has that, I’m using BallisticsARC, which does) till the range profile is what you prefer, then boresight to ‘make it so’. It will be a negative number, fairly close to your sight height. Then a card or sticky note with two dots the Elevation Offset distance apart, rifle leveled and clamped, move card till the lower dot is on the boresight laser dot, then adjust scope till it’s on the upper dot.

Of course all kinds of other factors will make this no good for more than a coarse battle zero. But at least all the new gear in the safe is at some reasonable settings till you can get proper dope at the range (which you already did, so you’re done, right?).

Fun stuff.
 
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#28
Skook and hugh - pretty much exactly what I was looking for, thank you.

rth - stupid is an interesting assertion considering what you said is factually incorrect. Check my edit.

With an impossible 0" optic height over bore (and any reasonable example of the height over bore measurement) the bullet is dropping past 100 when zeroed at 100. A typical set-up with any of the aforementioned calibers would need to be plugging along at something like 4000fps to be rising past 100, and even then, it's *maybe* 2/10ths of a MIL rise until it comes back to flat/equal with the 100yd zero. To
 
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#30
So let me see if I grasp the situation.
You take a scope or red dot centered from the factory. Mount it on a flat railed gun. Shoot at 36 yards and are having trouble with it being 2 1/2 inches high?

That is about right with being 2 1/2 above bore with the optic.
To get a hit in the zero you will go into the negative travel of the retical.

That would mean turning adjustment in the down direction.

Just set the gun to shoot a 50 yard zero and then play with your app.
 
#31
I have no interest in “an impossible zero height” or any other impossible to determine data.
I live and shoot in the real world. I would guess you live remote from a range and have VERY LITTLE shooting experience.
I shoot out my back door, my side and front door as well.
 
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#33
No trouble Snuby - rifle is zeroed and GTG. Was nothing more than a math question and wanting to know the formula, outside of what a standard ballistics calculator was capable of doing.

As to my zero and the inputs, it was as follows:

36yd zero - both rails are flat/0 MOA cant - LMT MRP/MWS

Kahles K16i
Spuhr 0 MOA Cant
Height over bore = 2.7"
5.56 - Required 3.3 MILs UP from factory/turret 0

NF ATACR 1-8
Spuhr 0 MOA Cant
Height over bore = 2.625"
7.62 - Required 4.6 MILs UP from factory/turret 0
 
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#34
rth1800 said:
He is not looking for answers, he wants a debate.
Click to expand...

The question has been answered.

You're the one that has interjected items that had nothing to do with the question - and erroneous at that.

In addition you resort to ad hominem, when your comments about a bullet and some mythical 'modern trajectory' completely belie the actual reality of ballistics.

Since you asked for a real example - here are 2 screenshots from my Shooter app.

First one is my .308 TacOps Delta 51, second is my Defiance Deviant/Krieger barreled 6.5 Creedmoor - both zeroed at 100 yards. The first column next to the yardage shows the descending trajectory past 100 yards.

The .308 impact is 1.1" lower at 150yds than the 100yd zeroed impact. The 6.5 impact is 0.8" lower at 150yds than the 100yd zeroed impact.

You must have some really amazing 6CM loads if you're zeroed at 100 and have a higher impact point at 150.

308.jpg


6-5.jpg
 
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#35
Yama Arashi said:
No trouble Snuby - rifle is zeroed and GTG. Was nothing more than a math question and wanting to know the formula, outside of what a standard ballistics calculator was capable of doing.

As to my zero and the inputs, it was as follows:

36yd zero - both rails are flat/0 MOA cant - LMT MRP/MWS

Kahles K16i
Spuhr 0 MOA Cant
Height over bore = 2.7"
5.56 - Required 3.3 MILs UP from factory/turret 0

NF ATACR 1-8
Spuhr 0 MOA Cant
Height over bore = 2.625"
7.62 - Required 4.6 MILs UP from factory/turret 0
Click to expand...

My bad.
Thought you were having a directional problem. I have firearms used in short range applications from 16-100 yards in comp.

Lowest possible mount makes it easier.
 
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#37
rth1800 said:
You ask nonsensical questions and changed them as you went along. You received nonsensical replies.
Click to expand...
Although he didn't quite know how to phrase it at first, the question was deciphered and answered.

When a mechanical offset is used, a one yard zero is not an impossible zero. Determining the drop of a round from a level firing position that is perpendicular to the pull of gravity is not an impossible solution.

None of this was deciphered or answered with your help, quite the opposite in fact.
 
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#39
I could have simply asked "If my height over bore is 2.625", and I'm shooting a 150gr bullet at 2700fps; and assuming the optic is mechanically centered, how much elevation will I need to dial up to be zeroed at 36yds?" - but I wanted to know if there was a specific equation to determine such, or if there was a way to get a ballistics program to calculate it.
 
#41
Yama Arashi said:
I could have simply asked "If my height over bore is 2.625", and I'm shooting a 150gr bullet at 2700fps; and assuming the optic is mechanically centered, how much elevation will I need to dial up to be zeroed at 36yds?" - but I wanted to know if there was a specific equation to determine such, or if there was a way to get a ballistics program to calculate it.
Click to expand...
Check any firing solution table and you are set
 
#42
LastShot300 said:
Check any firing solution table and you are set
Click to expand...

Not to drag this out, but that's the issue that prompted the original question.

There are no tables or ballistic calculators, that I've been able to find, that will tell you what your elevation/come-ups should be from the muzzle/point blank range. (after entering other pertinent information such as height over bore and caliber/muzzle velocity)

They generally require a zeroed range of 1 yard or greater, which then skews the rest of the numbers.

The Shooter app was the only one that allowed me to enter "0" as the zero range/distance, and calculated that I would need 2.3 MILs UP, whereas in actual shooting/zeroing, I needed 4.6 MILs UP. So, if the Shooter app was calculating correctly, my optic was factory zeroed below mechanical center, and I needed more come-up for a 36yd zero.

Otherwise, tables/ballistic calculators are not capable of calculating needed elevation to achieve zero at a particular distance, from the muzzle/point bank range, as they generally want a specified zero range beforehand (25, 36, 50, 100, 200 and so on) to calculate trajectories. And again, trajectory/ballistics after zeroing at a specific distance wasn't the intent of the original question.
 
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#44
Yama Arashi said:
The Shooter app was the only one that allowed me to enter "0" as the zero range/distance, and calculated that I would need 2.3 MILs UP, whereas in actual shooting/zeroing, I needed 4.6 MILs UP. So, if the Shooter app was calculating correctly, my optic was factory zeroed below mechanical center, and I needed more come-up for a 36yd zero.
Click to expand...
I ran it in JBM also. It said 2.2 MILS up.

It occured to me that, in this instance, determining what the actual drop is from a level muzzle is only part of the equation. What is missing is accounting for the value of the sight height in MILS at the distance desired.

In your example: 150 grain bullet at 2700 fps and 2.6" sight height. This bullet drops 2.2 mils from the muzzle at 36 yards.

However, we have set the line of sight level and parallel with the muzzle. In this instance, a sight height of 2.6 inches.
At 36 yards, 1 MIL is 1.296 inches....

If we divide the actual sight height in inches (2.6 inches) by the MIL value in inches for this distance (1.296 inches), we get 2.029 MILS.

2.029 MILS + 2.2 MILS = 4.22 MILS, which is really close to your actual come up.
 
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#45
Skookum said:
2.029 MILS + 2.2 MILS = 4.22 MILS, which is really close to your actual come up.
Click to expand...

THERE's the brain matter I was trying to find Skookum, thank you! I had been trying to calculate the MIL values at the zeroed distance doing some extrapolating from the standard 1 MIL = 3.6" at 100 yards etc., but hadn't been able to get it fully dissolved with all other variables involved.


rth1800 said:
OK, I am being serious here. What is the purpose/advantage of doing it this way?
Click to expand...

If you're referring to all the hemming and hawing on my part as to the math - it was simply wanting to know how to formulate the equation, and to see if it was matching up with my actual results; as well as the why or why not - just like you would calculate trajectory with a ballistics calculator, and verify your results, and adjust accordingly as needed. I wasn't able to do/verify what I was trying to do with ballistic calculator constraints.

If you're referring to the 36yd zero, it's just a matter of the specific rifle/optic combination and filling a certain role - just for the hell of it if anything.

With this particular set-up, the ATACR 1-8 acts as a red dot when dialed down into the lower magnification, and dialed up offers some PID as well as a useable reticle for holds. The elevation turret is capped, although the cap can be left off.

In comparison to the other ATACR turrets and reticles, this particular 1-8 optic leaves a lot to be desired if you are trying to use it in the same manner as the larger magnification scopes for gnats ass precision, dialing and distance. The center dot is .35 MILs and the entire center quadrant is 2 MILs.

This is more set-up as a semi-precision battle rifle. With a 36yd zero, I can put the center dot on target and hit within 3.8" up or down out just past 300 yards. Anything beyond that I would need to dial up the mag and know my hold values anyway.

DSC_7084_2-1-1024x704.jpg


DSC_7077_2-1.jpg
 
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#46
Yama Arashi said:
I think all my explaining is making the actual question more complicated than it is. :LOL:

I'm not questioning what a particular zero range will accomplish, if it can be achieved, or what the trajectories/holds etc., will be after setting zero.

More along the lines of, can a ballistics calculator tell you what elevation will be required to achieve a particular zero? (In the same way it can tell you what the required elevation will be for a particular distance *after* you've already input a set zero distance) It doesn't seem like they're designed or able to do so with the usual inputs. Or is there a mathematical formula/equation for being able to figure it out without actually shooting it?

Probably a question no one has bothered asking or needed to ask, for good reason. :rolleyes:

Using the Shooter app for example, which is the only one that will allow me to zet '0' as the zeroed range - zeroing the 7.62/150gr rifle/optic combination at 1yd would require 52.1 MILs of come up. Calculator says 36yds would require 2.2 MILs of come up, whereas it took me 4.6 MILs of come up to be zeroed at 36.

So *is* the calculator actually working correctly in this regard, and I needed more elevation to zero because of where the erector/reticle was factory set at 0 on the elevation turret in relation to all the other parameter inputs? Or is a ballistics calculator simply incapable of estimating what a zero distance will require in click elevation from the muzzle, in conjunction with the height over bore and bullet weight/velocity, without having a pre-established zero range?

Yes, I have, can, and will, just shoot the damn thing though............
Click to expand...

No, just bore sight it and shoot at whatever range you intend to zero it.
Theres no possible way the calculator can spit out a "comeup" for a scope not zeroed to a rifle. Regardless of what inputs you give it.
Theres probably not a way you or anyone could even calculate it.
 
#48
Skookum said:
I ran it in JBM also. It said 2.2 MILS up.

It occured to me that, in this instance, determining what the actual drop is from a level muzzle is only part of the equation. What is missing is accounting for the value of the sight height in MILS at the distance desired.

In your example: 150 grain bullet at 2700 fps and 2.6" sight height. This bullet drops 2.2 mils from the muzzle at 36 yards.

However, we have set the line of sight level and parallel with the muzzle. In this instance, a sight height of 2.6 inches.
At 36 yards, 1 MIL is 1.296 inches....

If we divide the actual sight height in inches (2.6 inches) by the MIL value in inches for this distance (1.296 inches), we get 2.029 MILS.

2.029 MILS + 2.2 MILS = 4.22 MILS, which is really close to your actual come up.
Click to expand...


Just a note the bullet weight (150 grain) has zero to do with the formula, SOB+gravity drop (TOF). And of course, does NOT account for receiver/mechanical issues or shooter offsets (post #47). The only real value for most shooters, you'll know who much scope travel will be used up to zero when planning bases etc..

The secondary logic and value of this, is very similar to knowing your loop clearance needed.
 
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