Actual dope data not lining up with ballistic calculator?

[CALLSIGN Loot Drop]

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:

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

(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:

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?

 

[bruiz86]

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.

 

[CALLSIGN Loot Drop]

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.

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.

 

[DFOOSKING]

Your written trajectory looks like a 308 chart. I'd be willing to bet money your 400yd is around 2.4 mils....not 1.7

 

[bruiz86]

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

 

[CALLSIGN Loot Drop]

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

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.

 

[6.5SH]

I also doubt your sight height is 1.5", 2.7" is common with an AR.