I have the Hornady 4DOF app and want to adjust my axial form factor but I don’t have a chronograph to get my true MV. So I will have no clue whether my vertical spread being off is from having a different MV than the box or whether it is actually the drag curve abnormalities that the axial form factor is supposed to account for. Any suggestions?
Axial Form Factor
- Thread starter TM1107
- Start date
It shows in the App, you need to figure the group center, and if you feel you have a high vertical spread, do what you can to minimize it.
What range are you shooting ?
You need a group center and large enough sample size, if you are "seeing" the vertical you probably have an issue in the load.
Factory or Handloads ?
What are you using, more information will get you better answers to your questions
Distance
Load
Group Size
There is no free lunch you have to do your part too, the computer does not shoot it, only predicts where the shots should go.
What range are you shooting ?
You need a group center and large enough sample size, if you are "seeing" the vertical you probably have an issue in the load.
Factory or Handloads ?
What are you using, more information will get you better answers to your questions
Distance
Load
Group Size
There is no free lunch you have to do your part too, the computer does not shoot it, only predicts where the shots should go.
Well I’m using an R700 SPS in 6.5 CM with factory 140 ELD-M ammo and have access to 500yds plus. However this question is more hypothetical and I wonder if I wasn’t clear. So when I watch the 4DOF how to from Hornady they chrono their ammo with a lab radar, then shoot a 5 shot group at distance (I think 4-500yds). Their group is high compared to what the app called for, but because they had an accurate MV, they adjust axial form factor. I don’t have that luxury so I don’t know what I need to adjust if I happen to be off.
Your zero range is, say 100. .15" high is not zero. That is high. You need to have an absolute ZERO drop or rise from your POA range. This has been hammered into me more times than I can remember. Adjust the range to match your POA.
Shoot at 300 with an estimated dope and adjust your MV to match your POA, that will get you close, but the farther you can make adjustments the better.
If you have left or right dispersion that is inbetween clicks at zero range, bummer, 4DOF does not have anything to counter this, you have to keep notes and remember to compensate.
Really should try adjusting the MV to the POA at 500, then do an axial at 800ish. If you are getting vertical stringing not actual groups, then other issues are at play (shooter, variable wind, mirage, incorrect distance to target) and you will not get good numbers. Garbage in, garbage out.
Having said all that, I have only managed to get one of 4 rifles to work well with 4DOF and the zero angle and axial. Three of them are outside the acceptable specs for one of the two and just when I think I have it ironed out, then the next range session my dope is crap.
Shoot at 300 with an estimated dope and adjust your MV to match your POA, that will get you close, but the farther you can make adjustments the better.
If you have left or right dispersion that is inbetween clicks at zero range, bummer, 4DOF does not have anything to counter this, you have to keep notes and remember to compensate.
Really should try adjusting the MV to the POA at 500, then do an axial at 800ish. If you are getting vertical stringing not actual groups, then other issues are at play (shooter, variable wind, mirage, incorrect distance to target) and you will not get good numbers. Garbage in, garbage out.
Having said all that, I have only managed to get one of 4 rifles to work well with 4DOF and the zero angle and axial. Three of them are outside the acceptable specs for one of the two and just when I think I have it ironed out, then the next range session my dope is crap.
Last edited:
There is no great answer to this. Without knowing your MV at some point you would just have to assume it is correct before adjusting AFF.
What distance did you shoot for your dope? If less than 500 adjust the MV. Then past 500 adjust form factor. At 500 yards and a 140 eld 25 fps is worth about a tenth of a mil and .05 axial form factor is only work a couple hundredths of a mil.
Basically what I am saying is inside 500 your MV is the main driver of drop. Past that form factor drives it much more so I wouldn't mess with axial form factor until 800+.
Basically what I am saying is inside 500 your MV is the main driver of drop. Past that form factor drives it much more so I wouldn't mess with axial form factor until 800+.
Similar threads
Range Report
Wild dope truing AB and 4dof. What is reasonable?
