Garmin or ballistic app is wrong?

[Remington92]

I’m getting my rifle fine dialed for hunting season and left scratching my head comparing my Garmin xero to what ab mobile is giving me for dope. My rifle is a tikka ss 6.5prc chopped to 22” with a scythe on the end of it and I’m running factory 143eldx precision hunter. My Garmin gives me an average of about 2850 and the box says 2960 which jives with the shorter and slower tikka barrel. Out to 400yds my adjustments are dead on. Next target I reached out to is 800 yds and to get ab mobile to give me the correct elevation I had to slow down to 2780 or an extra 0.3 mil. I’m at 3200ft da for reference.

Is the garmin that far off or is there something goofy with what ab is feeding me? Also anyone ever have issues that you have to reload ab a couple times to get consistent values

 

[Wrench]

What your group size, wind, DA, DOF, BC....and have you tall targeted the rifle?

 

[Macintosh]

If your adjustment values are off a little that would do that—tall target should tell you.
Are all of your inputs correct? DA mainly, but also sight height, etc will affect it some.
BC is also going to be off—did you use a litz drag curve, or?

Fwiw Ive been starting with box velocity and using the ab truing function using all three distances, and it does work to get good dope from near to far…without a chrono I have nothing to compare it to though. Maybe thats a benefit?

 

[Remington92]

Group size today was just under 8” at 800yds. Not sure what tall targeting is but I did hang a piece of cardboard bout 3’ wide by 4’ tall with a target in the middle which is how I got my low impacts at 800. I checked DA populating on the app against my kestrel and that was good. Level open prairie without a stitch of wind today. I used the g7 bc that pre populated for the 143eldx in ab mobile. Double checked sight height as well. 1.5” with T084 rings is what I got.

 

[Macintosh]

How many rounds are you shooting at each distance to determine where group is centered?
How perfectly are you zeroed, and based off a 3,5, 10, etc round group?

 

[sveltri]

Is your scope height value correct?

 

[hereinaz]

Way more goes into truing ballistic solution than just velocity. Your Garmin’s velocity is not wrong. You’ve now seen it’s not as simple as putting in a couple values. Besides velocity, the BC of your bullet and rifle needs to be tweaked. BC is not a fixed number, it varies according to how the bullet may deform and by velocity.

Also check:

— your scope over bore height
— your turret to see if you dial one MOA or MIL and it actually moves it one full value. Scope turrets can be off by a few percentages, and more in worse situations.

And, many newish shooters find variation from day to day. The long range zero can easily vary because a shooter builds their position differently and control recoil differently from day to day.

 

[Remington92]

Way more goes into truing ballistic solution than just velocity. Your Garmin’s velocity is not wrong. You’ve now seen it’s not as simple as putting in a couple values. Besides velocity, the BC of your bullet and rifle needs to be tweaked. BC is not a fixed number, it varies according to how the bullet may deform and by velocity.

Also check:

— your scope over bore height
— your turret to see if you dial one MOA or MIL and it actually moves it one full value. Scope turrets can be off by a few percentages, and more in worse situations.

And, many newish shooters find variation from day to day. The long range zero can easily vary because a shooter builds their position differently and control recoil differently from day to day.

ok thanks I’ll tweak the bc and see if that’ll get me closer, I thought I’d read here before that it’s not best to tweak bc and rely on velocity which is why I started there.

 

[Remington92]

So I tweaked the bc and to get it to match my dope at 800 I had to drop the bc from .292 to .25 which seems waaaayyy off

 

[Wrench]

Step one is to tall taget test the tracking. You need to know you're running true to the click.....and is there any chance you have yds/meters mixed up?

 

[hereinaz]

So I tweaked the bc and to get it to match my dope at 800 I had to drop the bc from .292 to .25 which seems waaaayyy off

When it is that far off, start with velocity, it if matches out to 800. Tweak the BC just a little bit as necessary.

Also, check you scope. Put a tall target with a grid on it and check if you can dial it 10 moa or 4 mil and see if the clicks equal the distance you dialed.

Confirm your height over bore as well.

 

[Remington92]

I’m starting to think there’s something wrong with the ab app. I don’t get consistent reading each time i open it re entering same environmentals.

I just tried shooter and put in hornadys Mach based bc’s and it’s spot on at 2850

 

[Shortschaf]

I’m starting to think there’s something wrong with the ab app. I don’t get consistent reading each time i open it re entering same environmentals.

I just tried shooter and put in hornadys Mach based bc’s and it’s spot on at 2850

Dont mess with the AB library BC's. They are doppler verified, and unlikely to be the issue

If you aren't measuring environmentals (clicking the button on the app doesnt count), that is your issue

That's assuming your zero, shooting, group size, scope tracking, etc are all good to go

 

[hereinaz]

I’m starting to think there’s something wrong with the ab app. I don’t get consistent reading each time i open it re entering same environmentals.

I just tried shooter and put in hornadys Mach based bc’s and it’s spot on at 2850

The odds that the problem is with the AB app are pretty slim to none. Problems I have seen are user error with input or ultimately a scope tracking error.

If the other ballistic engines are right, then my suggestion is to start over again with a new gun in AB, and carefully make inputs. That is easier than tracking down any errors that you may have inadvertently caused.

I have goofed up a rifle data before and just started over, back when I was learning.

 

[Remington92]

I have a kestrel 5700 to check environmentals on, what I’m saying is I get different readings from a when I run the calculations everything else being the same. Example 3100da 41*f 1000yds one time I may get 7.8mil the next I may get 6.3 mil

I’ll get deleting the rifle out and reentering it to see if that solves it though

 

[hereinaz]

Forgot to add that Shooter is easier and if it is working, stick with it. AB does get more complicated with some things that make little difference inside 800z

 

[hereinaz]

I have a kestrel 5700 to check environmentals on, what I’m saying is I get different readings from a when I run the calculations everything else being the same. Example 3100da 41*f 1000yds one time I may get 7.8mil the next I may get 6.3 mil

I’ll get deleting the rifle out and reentering it to see if that solves it though

It saves the last environmentals in mine.

And, there isn’t a field for DA in my version. Not sure if you are putting in DA for altitude and combining it with baro pressure and temp, getting you compounded environmentals.

DA accounts for temp, station/absolute pressure and humidity.

 

[hereinaz]

Screen shot the environmentals and then the dope where you are getting different drop, and post them. I am curious. And we’ll be able to help possibly.

 

[Remington92]

This is what I get with mine. If say I switch out my prc and look at my mk12 then back into the prc and enter same environmentals it’ll give me different dope sometimes. Or if I tweak velocity or bc then put it back I’ll get different outputs. I’ll fiddle with it and see if I can get it act up for me again

 

[hereinaz]

Weird. Start saving screen shots to confirm..

Or just start with a new gun and see if it goes away, lol. I resort to the power button as my IT fix for everything. It’s usually user error, hahaha.