Actual dope data not lining up with ballistic calculator?

C

CALLSIGN Loot Drop

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Minuteman
Sep 25, 2025
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3
Ohio
#1
Sorry if this question is always asked but wanted to see what I’m doing wrong.

I’ve got a 16” Geissele GFR 6ARC rifle that I took out to 900 yards recently. 100 yard zero, sub-MOA grouping gun. I was able to build a rudimentary dope with Hornady 108gr ELDM factory loads shown here:

image.jpg


However, when I plug my data and estimations into Hornady’s 4DOF, the come up values don’t line up exactly:

IMG_0807.png

(The above atmospherics are actual reported conditions on the day I did the shooting, though I pulled the numbers from online weather apps so not sure how exact but definitely accurate enough)

I’m mainly questioning the the 400yd value. I swear I was at 1.7 on my scope but I could have actually been 2.7; I don’t have the opportunity to go back out to that range for a while to confirm.

Here are the rifle settings I entered:

IMG_0808.png


Disclaimer: I have not chrono’d the load, but based on this estimated MV enough of the Hornady’s calculated values are close to what I actually got. Sometime in the next 2 weeks I should be able to chrono the load.

The question: Do the numbers on my actual dope make sense? If so, why is there such a big jump from 300 to 400? Or do you think I’m stupid wrote the wrong number down?
 
#2
Good idea would be to read about gravity ballistics. It will help simplify what you're trying to do. Quick look at your data and it's inaccurate. I'm not gonna word this correctly but your gaps from one yardage to the next should gradually grow and never be less than the previous adjustment. Take 5 6 7 for example. From 5 to 600 you adjust 1.6 but from 6 to 700 it drops to 1.2. That is not possible as gravity is constant and the bullet is slowing down.
 
#3
bruiz86 said:
Good idea would be to read about gravity ballistics. It will help simplify what you're trying to do. Quick look at your data and it's inaccurate. I'm not gonna word this correctly but your gaps from one yardage to the next should gradually grow and never be less than the previous adjustment. Take 5 6 7 for example. From 5 to 600 you adjust 1.6 but from 6 to 700 it drops to 1.2. That is not possible as gravity is constant and the bullet is slowing down.
Click to expand...
Yea that part also confused me; the splits make no sense to me, either.

Do you have any way to virtually correct this or do I just have to hit the long range again and keep trying (with Hornady’s 4DOF as a starting point)? I really want to get out somewhere with a chrono to plug in those values to 4DOF regardless.
 
#5
I would pay the 10 bucks or whatever it is for the gravity ballistics app. You don't need a chrono or anything beyond a solid 100 yard zero. Takes a little math or you can just use that app but it will give you your next yardage TRY dope. After you're all done shooing then you can go back and true your ballistic apps
 
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#6
bruiz86 said:
I would pay the 10 bucks or whatever it is for the gravity ballistics app. You don't need a chrono or anything beyond a solid 100 yard zero. Takes a little math or you can just use that app but it will give you your next yardage TRY dope. After you're all done shooing then you can go back and true your ballistic apps
Click to expand...
Cool, will give it a look.

Does it modify the TRY dope in real time? For example, let’s say it says my TRY is:

100 - 0
200 - 0.6
300 - 1.7
400 - 2.9
500 - 4.4

And when I go to shoot my actual drop to 300 is:

100 - 0
200 - 0.5
300 - 1.3

Will it automatically adjust my 400 and 500 to be less than 2.9 and 4.4, respectively? I ask because I don’t have consistent access to a range that goes beyond that far so when I do get out to one I don’t want to be wasting too much ammo finding out that the initial TRY dopes are off.
 
#9
CALLSIGN Loot Drop said:
Cool, will give it a look.

Does it modify the TRY dope in real time? For example, let’s say it says my TRY is:

100 - 0
200 - 0.6
300 - 1.7
400 - 2.9
500 - 4.4

And when I go to shoot my actual drop to 300 is:

100 - 0
200 - 0.5
300 - 1.3

Will it automatically adjust my 400 and 500 to be less than 2.9 and 4.4, respectively? I ask because I don’t have consistent access to a range that goes beyond that far so when I do get out to one I don’t want to be wasting too much ammo finding out that the initial TRY dopes are off.
Click to expand...
Yes it adjusts as you go. Water line your steel and the TRY numbers will get you within a click or 2.
 
#10
A couple things about 4dof:
- Always use the 4dof, not the bc calculator. The bc calculator hasn’t worked well for me in the past but the 4dof side is very good.
- Watch the videos from Hornady and follow the setup process they provide, things should line up better.

As mentioned above, your sight height appears to be wrong. Double check your inputs and re-enter your data from the last range session (including the atmospherics from that day). Adjust your velocity to line up to about 600 yards and then adjust your Axial Form Factor after that. You should be very close. It already looked close from 700-900 yards.
 
#13
CALLSIGN Loot Drop said:
Disclaimer: I have not chrono’d the load, but based on this estimated MV enough of the Hornady’s calculated values are close to what I actually got. Sometime in the next 2 weeks I should be able to chrono the load.
Click to expand...
Whoa...I missed this first time around. Hornady's box speed for 108 ELD-M factory ammo is 2,750

Where did you come up with 2550 if you didn't chrono?
 
#14
for factory ammo, i always put the box numbers (fps, bc) into the ballistic calculator and ensure the output (drop, windage) come pretty close to the box numbers for a sanity check (ie i didn't goof up the bc etc). then i put in the actual chrono speeds and go from there.
 
#16
The above plus... I'm leaning towards a dial-reading or data-recording error.

1) It's easy enough to mistake 2.2 or 2.7 mils for 1.7 mils on some dials if you're not paying close attention.
They are all "one big hashmark plus two little ones."

2) How many shots to establish dope at each range? That concept is the noise in your trajectory measurements which 4DOF doesn't have. If reality was 1.7 or 2.7 mils then you've got a lot of slop in your measurements.
1760984362502.png
1760984415090.png
 
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#18
Gemsbok said:
The above plus... I'm leaning towards a dial-reading or data-recording error.

1) It's easy enough to mistake 2.2 or 2.7 mils for 1.7 mils on some dials if you're not paying close attention.
They are all "one big hashmark plus two little ones."

2) How many shots to establish dope at each range? That concept is the noise in your trajectory measurements which 4DOF doesn't have. If reality was 1.7 or 2.7 mils then you've got a lot of slop in your measurements.
View attachment 8790876View attachment 8790877
Click to expand...
Nice graphics! It really makes the discrepancies pop up. Are you building these in Excel or is this something else?
 
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#19
6.5SH said:
I also doubt your sight height is 1.5", 2.7" is common with an AR.
Click to expand...
Ah good catch, I only put the height from mount to center of optic tube and forgot to add center of bore to top of rail.

davsco said:
isn't this step one in calculating ballistics? or just shoot it and see what it does at various yardages.
Click to expand...
One of the youtube videos I saw about building dope without a chrono is shooting at various ranges and then playing around with the MV slider until the calculated drops on the app line up with what you're seeing in the real world.

Gemsbok said:
The above plus... I'm leaning towards a dial-reading or data-recording error.

1) It's easy enough to mistake 2.2 or 2.7 mils for 1.7 mils on some dials if you're not paying close attention.
They are all "one big hashmark plus two little ones."

2) How many shots to establish dope at each range? That concept is the noise in your trajectory measurements which 4DOF doesn't have. If reality was 1.7 or 2.7 mils then you've got a lot of slop in your measurements.
View attachment 8790876View attachment 8790877
Click to expand...
Thanks for helping visualize this! Definitely makes it seem like I read 2.2 as 1.7 like you said, since big line + 4 little lines.

I didn't have a lot of ammo with me but I shot maybe 3-5 rounds per distance. The 700-900 targets had those flashing lights to indicate impact so those actually were easier to spot than 300-500. Unfortunately the plates didn't have water lines and seemed like they hadn't been repainted in a while which definitely made spotting impacts harder.
 
#20
I adjusted the sight height to 2.7 and kept the MV at 2550 and got this:

IMG_0827.png


When I drop the MV to 2520 things appear to line up better (see below), does that velocity seem consistent with a 16” + suppressor?

IMG_0828.png
 

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#21
It might be. Make friends with someone who has a chronograph.
The use of a water line or precise impact on paper gives an actual measurement.
I've been in the same predicament, very shot up targets with no water line and no down range access. A trick that might work for you is find a smaller rock, stick, impression in the dirt near your target. Use your reticle to measure it. A hit on a ~1 MOA rock at 600+ tells you more than a "ding" on a larger lead colored piece of steel you can't clearly see.
 
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#22
Shit in shit out. Fix your variables and you will get predictable results that match up with your actual dope. MV, DA and BC the big 3 . Everything else is small adjustments. Focus on the big 3 first then refine. I would bet all 3 or yours are wrong.

You can't trust the bc or mv on the side of a box. Find the AB trued value or the custom curve. This is the start of your education on why 4dof is for amateurs and pros run AB.
 
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#24
What I have learned is that the more factors you can account for and the more real world DOPE you can input, the more precise any ballistic calculator is going to be. I like 4DOF. But I just also got Gravity Ballistics. Way easier to use than some others. Directions are to zero at 100 yards. And true, not a lot of people have access to 200 yards or more. Or, at least, not easily. It's at least two to three hours, depending on traffic to get to a long range where I could get past 100 yards. The closest 100 yard range to me is the Riflegear in The Colony, (Texas.)

Anyway, with Gravity Ballistics, you input ammo and bullet type just to, in the words of Offspring ("You got to keep them separated") differentiate which load and rifle from another profile. But those numbers are not needed for calculation. If your MV is stable, then you can zero at 100.

(I know that when I zero, all the ammo data doesn't mean anything. What matters is aligning point of aim with point of impact. The ammo data only matters in a number of calculators when generating dialing and holding solutions.)

Use any means to dial or hold for 200 and see where it lands. If your elevation was good, you confirm that setting and the rest of the HUD changes using that correction. For example, not many situations where 2 MOA is needed for 200 yards. Usually a little less. 1.8 is a good start. You could use Shooters' Calculator, which is free, to print their chart, a try DOPE range card, if you will.

Another thing I have learned is that the farther you can shoot and confirm, the more accurate your DOPE and calculator will be. Also, other factors can be affecting the trajectory that cannot be accounted for in a solver. For example, a full value gust at 3 o'clock at, say 350 yards, is causing a result not quite anticipated.
 
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#26
jthor said:
Nothing wrong 4DoF as a solver, it’s very trustworthy solver on the 4DoF side given you input correct info and true the Axial form factor if needed. The statement made above incredibly incorrect.
Click to expand...
I believe you, but using some calculator specific created “axial form factor” that needs to be “ trued”along with the use of altitude as a nod to shooters that are not willing to understand the basics of DA doesn’t bring me into the 4 DOF fold. I have no particular allegiance to a solver, but the useability of AB especially now with the Quantum, along with Doppler CDM/PDM libraries, added to the very basic bordering on ridiculous questions about 4 DoF inputs from shooters I know who attempt/use it continues to lower my confidence. I have tried myself, it’s not very intuitive. The constant “no calculator lines up well and they all have to be trued” is disingenuous and misleading for most shooters. People love blame the math when the answer to their poor performance is looking back from the mirror. None of these engines are particularly complex from a real math nerd point of view, considering what most of us are trying to accomplish. Case in point, people constantly tell me the rocket scientist is wrong while they seize on altitude vs DA as a critical variable.
 
#27
Emerson0311 said:
I believe you, but using some calculator specific created “axial form factor” that needs to be “ trued”along with the use of altitude as a nod to shooters that are not willing to understand the basics of DA doesn’t bring me into the 4 DOF fold. I have no particular allegiance to a solver, but the useability of AB especially now with the Quantum, along with Doppler CDM/PDM libraries, added to the very basic bordering on ridiculous questions about 4 DoF inputs from shooters I know who attempt/use it continues to lower my confidence. I have tried myself, it’s not very intuitive. The constant “no calculator lines up well and they all have to be trued” is disingenuous and misleading for most shooters. People love blame the math when the answer to their poor performance is looking back from the mirror. None of these engines are particularly complex from a real math nerd point of view, considering what most of us are trying to accomplish. Case in point, people constantly tell me the rocket scientist is wrong while they seize on altitude vs DA as a critical variable.
Click to expand...
I’m not entirely sure/don’t understand what you’re trying to explain here as every solver requires:
- user inputed data
- current/updated environmentals.
- truing

You treat the axial form factor no different than if you are truing a G1/7 BC on any solver.
Truing is also something that needs to tested regardless if you need to change values or not as a confirmation if shooting long range.

Between AB Quantum and 4DoF neither is hugely more complicated than the other. Both require the user to input correct rifle and load data and then true up if needed. Except for the CDM, I can’t modify it like I can with the 4DoF Axial Form Factor in order for it to line up. It either does or doesn’t. In my case I have not gotten the AB DSF to work like in a similar fashion to 4DoF AFF.
 
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