When ballistics and moa don’t match

[huntin24/7]

Anyone had a rifle/scope setup that’s ballistics never match drop/moa? I have a 7mm with a vx 3 or 4 scope)can’t remember exactly which. I’ve shot 168 Bergers and now 160 accubonds. It’s always hit 1-2 moa higher than ballistics calculators say it should, especially from 300+ yards, with its speed, ballistic coefficient, etc. I verify it at all distances anyways so not that big of a deal. Just wondering if that happens very often for others. Ive never had a custom cds dial so it makes me kind of question how accurate they actually are.

 

[Deez Nutz]

Lots of variables and always good to true data. How are you obtaining your velocity?

 

[huntin24/7]

I have a garmin pro chronograph.

 

[Fire_9]

Have you had other rifles match up correctly?

 

[huntin24/7]

Have you had other rifles match up correctly?

I’ve only ever had 2 rifles with moa turrets. The other one has been so consistent since I sighted it in that i haven’t really compared. Groups in the rifle I previously mentioned are good too and it tracks well once I get moa figured out.

 

[Forkyfinder]

Yes. And every time was an error or data i left out of the calculator.

Suspect that barometric pressure might be incorrect? If you are using that you need to use an "uncorrected" value.

 

[Deez Nutz]

If you are using a drop chart, which is essentially the same as a CDS type turret (meaning not using real time data like density altitude, temp, pressure, relative humidity, etc) then do the best you can to enter the most accurate information you have. That should get you on paper. Then use that data to true your drops at different ranges. Once you have that verified, you have trued your drops in that specific set of conditions, but different sets of conditions will alter your dope. Play around with a ballistic calculator by entering different elevations, different temperatures, etc. until you have a good idea of how those factors will alter your drop in different conditions.

Bottom line is using a drop chart or a CDS dial you are using an "average" data set that should get you closeish for short to mid range shots.

 

[Fire_9]

Yes. And every time was an error or data i left out of the calculator.

Suspect that barometric pressure might be incorrect? If you are using that you need to use an "uncorrected" value.

This was going to be my suggestion too. You need station pressure

 

[huntin24/7]

Yes. And every time was an error or data i left out of the calculator.

Suspect that barometric pressure might be incorrect? If you are using that you need to use an "uncorrected" value.

I do put in an average barometric pressure for our area. Can’t think of anything I’m missing but very well could be. This is mostly using Hornady ballistics.

 

[Fire_9]

I do put in an average barometric pressure for our area. Can’t think of anything I’m missing but very well could be. This is mostly using Hornady ballistics.

If you're getting it from your weather app then this is it. I don't know what your elevation is but punch the highlighted numbers in for your area and run the numbers again. I would also double check your sight height

 

[DFS]

I always attribute it to BC variation. As long as I can replicate it I don’t worry about it.

 

[Forkyfinder]

I do put in an average barometric pressure for our area. Can’t think of anything I’m missing but very well could be. This is mostly using Hornady ballistics.

What pressure you putting in?

The local reported barometric pressure is typically corrected for sea level. So that it can be seen on a "relative" scale - so that everyone can see if pressure is "high" or "low"

Ie "std" pressure is 29.92 (sea level) - uncorrected pressure at 4k elev is 25.84.

 

[Forkyfinder]

If you're getting it from your weather app then this is it. I don't know what your elevation is but punch the highlighted numbers in for your area and run the numbers again. I would also double check your sight height

View attachment 416123

Beat me to it

 

[huntin24/7]

If you are using a drop chart, which is essentially the same as a CDS type turret (meaning not using real time data like density altitude, temp, pressure, relative humidity, etc) then do the best you can to enter the most accurate information you have. That should get you on paper. Then use that data to true your drops at different ranges. Once you have that verified, you have trued your drops in that specific set of conditions, but different sets of conditions will alter your dope. Play around with a ballistic calculator by entering different elevations, different temperatures, etc. until you have a good idea of how those factors will alter your drop in different conditions.

Bottom line is using a drop chart or a CDS dial you are using an "average" data set that should get you close for short to mid range shots.

I try a pretty large variety of variables to see if I’m missing anything. In this example, I’m shooting 160 accubond(bc of .531) at an average of 2890 fps with a sight in of 0-.5” high at 100 yards. Everything I check for different variables puts me at around 4” low at 200 and around 12” low at 300. I’m right at 1.75 low at 200 and 9” low at 300. As I mentioned, it’s an easy enough adjustment, and maybe my scope just isn’t exact on the 1/4” per click at 100 yards etc.

 

[huntin24/7]

What pressure you putting in?

The local reported barometric pressure is typically corrected for sea level. So that it can be seen on a "relative" scale - so that everyone can see if pressure is "high" or "low"

Ie "std" pressure is 29.92 (sea level) - uncorrected pressure at 4k elev is 25.84.

For the heck of it, I checked all the same data but with a barometric pressure of 24 and 30 at 2100 elevation where I live and it only showed a half inch difference at 300 yards. I’m certainly no expert though so interested in anything you guys can add.

 

[Deez Nutz]

I try a pretty large variety of variables to see if I’m missing anything. In this example, I’m shooting 160 accubond(bc of .531) at an average of 2890 fps with a sitting of 0-.5” high at 100 yards. Everything I check for different variables puts me at around 4” low at 200 and around 12” low at 300. I’m right at 1.75 low at 200 and 9” low at 300. As I mentioned, it’s an easy enough adjustment, and maybe my scope just isn’t exact on the 1/4” per click at 100 yards etc.

You can always fudge your BC or velocity in your ballistics calculator to get it to match your drop. But if you shoot a group one day at 1000 yds to find your drop, the next day if you use the same hold over to make the same shot, your point of impact will likely be different solely due to a change in environmental conditions. Hope that makes sense.

Also, would be pretty easy to verify your "clicks" if that is something you are second guessing. Zero at 100. Dial 10 MOA one way or the other, shoot a group, and measure.

 

[Forkyfinder]

For the heck of it, I checked all the same data but with a barometric pressure of 24 and 30 at 2100 elevation where I live and it only showed a half inch difference at 300 yards. I’m certainly no expert though so interested in anything you guys can add.

I try a pretty large variety of variables to see if I’m missing anything. In this example, I’m shooting 160 accubond(bc of .531) at an average of 2890 fps with a sight in of 0-.5” high at 100 yards. Everything I check for different variables puts me at around 4” low at 200 and around 12” low at 300. I’m right at 1.75 low at 200 and 9” low at 300. As I mentioned, it’s an easy enough adjustment, and maybe my scope just isn’t exact on the 1/4” per click at 100 yards etc.

When i ran that in strelok pro - it seemed to be within margin of error to match your in field results.

 

[huntin24/7]

View attachment 416127
When i ran that in strelok pro - it seemed to be within margin of error to match your in field results.

That’s definitely way more in line with what I’m seeing. I’ve always used Hornady ballistics, but I’ll have to give that a go. Thanks for running that!

 

[Forkyfinder]

That’s definitely way more in line with what I’m seeing. I’ve always used Hornady ballistics, but I’ll have to give that a go. Thanks for running that!

No problem.

I found that hornadys app was a POS, the UI sucks, and its easy for values to over ride others without explicitly saying.

Strelok was developed by a russian so you have to use some clever dark web tricks to get it. Ive heard some folks like AB but i didnt.