Noob! What am I doing wrong?

[Ffjmoore]

While on vacation at a ranch I set up a 20" steel plate that I could shoot at a max of 800yrds. I could not hit it for the life of me at 800 using the hornady calculator. I finally drove closer to 400 then backed up to 600 and then was finally able to hit at 800. Once I had the right dope I was able to hit every time.

The ballistics calculator was off by 1.5 mill or 43".

My question is how accurate are these usually and what variables could I be inputting wrong to make it that far off?

6.5cm 24" barrel shooting 140gr hornady bthp

My final elevation was 4.8mills
Hornady said 6.4 mill

 

[CoryT]

I don't see a velocity, zero range or BC/reference, so it's hard to say where you went wrong. For a 140g AMax at 2800fps zeroed at 100 under those conditions I'd expect about 5.4mil, I'd need 2950fps to get to 4.8 mil, so your "correct" elevation is a bit suspect already. Has the scope been calibrated?

 

[Roslyn]

The question is too open ended to provide a simple reply. You should check:

-- Scope zeroed at 100 yards? If yes, is that how you have it set up in the ballistics calculator?
-- Have you set the scope height over bore at the correct level? Just looking at the image would imagine is should be around 2.2-2.5 inches, but you should measure it properly and use the measured value.
-- Using G1 or G7 ballistic coefficient for the 140 rounds? Whichever you are using, be sure you are using the correct value for the 140s; and also haven't put the G1 figure into the G7 field or vice versa.
-- And obviously you need correct data in the calculator for the 140 rounds themselves -- weight, length, diameter.
-- Muzzle velocity input correctly?
-- Density altitude set up correctly? Is it a value you are entering yourself or is it being added automatically from barometric pressure and temperature?
-- Twist rate input correctly?

My guess is that you haven't got the scope height, or the G1/G7 BC, or the scope zero properly configured in the calculator. The other variables could make a difference but not likely 1.6 mils at that distance.

 

[Steel head]

We need speeds, BC used, altitude and air conditions to be of any help.
The Hornandy app is good but can be quirky at times.
From the screen shot pressure seems quite high for that altitude.
4.7-5 mils at 800 is a pretty normal range for 6.5’s.
My 260 is about 4.8 at 2300 altitude but pushing 130’s pretty fast.

 

[Ffjmoore]

Thank you. I'll go back and sort that stuff out and see what difference it makes.

 

[Ffjmoore]

Double checked the pressure and it was correct according to weather website. I don't have a kestrol. Measured my scope height and changed it to 2" from 1.5. Made no big difference in the output. The bc was a g1 and correct. I have not chronoed this particular round but it shoots similar to the 140 eldm and those are right at 2700 out of this barrel. Next time I'm at the range I'll chrono these and confirm my zero. Zero is the only think I can think of as to why it would be this far off. I have only zeroed at 100 but who knows what could have happened. I'll just double check.

 

[Punkur67]

I had the same issue with the 4dof app beyond about 500 yards. Used my kestrel calculator and was right on. Some calcs were up to 3 moa off

 

[Steel head]

Double checked the pressure and it was correct according to weather website. I don't have a kestrol. Measured my scope height and changed it to 2" from 1.5. Made no big difference in the output. The bc was a g1 and correct. I have not chronoed this particular round but it shoots similar to the 140 eldm and those are right at 2700 out of this barrel. Next time I'm at the range I'll chrono these and confirm my zero. Zero is the only think I can think of as to why it would be this far off. I have only zeroed at 100 but who knows what could have happened. I'll just double check.

At that altitude that pressure is certainly wrong unless it’s corrected for altitude and therefore wrong for using In a solver.
That and I’m guessing you’re speed is faster than you assume

 

[Steel head]

I had the same issue with the 4dof app beyond about 500 yards. Used my kestrel calculator and was right on. Some calcs were up to 3 moa off

I just plugged in all my data and dope from yesterday with my 260 and the Hornandy app was within a tenth Or two of my trued up kestrel at 775, 1050 and 1260 yards yesterday.

The OP is obviously suffering from garbage in= garbage out syndrome.

 

[Ffjmoore]

This is from today. I was there last week but the pressure is basically the same. Duh the op is suffering from garbage in garbage out. I'm trying to figure out what part of my data is garbage and causing the error. Like it says in the title, I'm new. I don't own a kestrel.

 

[Steel head]

Barometric pressure is adjusted for altitude and NOT what you want to use.
you want station pressure.

 

[Ffjmoore]

Barometric pressure is adjusted for altitude and NOT what you want to use.
you want station pressure.

Copy, thank you.

 

[isofahunter]

If you haven't watch the 4DOF video and follow to a T and you should have good results. As @Steel head said garbage in garbage out.

 

[Sig Marine]

As many have said, when numbers are off by a substantial amount, input is usually the culprit. Assuming that you have double and triple checked your inputs, two things that cause large errors that are overlooked by many shooters when making velocity adjustments based on scope elevations are scope tracking and target distance. Scope calibration - have you you done a "tall target" test to see if you have a correction factor that needs to be applied? Yardage - the distance to the target you are shooting to has to be correct, being off just 25 yards will account for the difference you are encountering.

I've used most of the ballistic programs available and they all (even the Hornady 4DOF) are within 0.2 MIL out to 1200 yards when inputs are correct.

 

[Long Range 338]

Typically the 4DOF program is very good and if you are shooting Hornady bullets it is spot on. Double check your data with another app or using JBM or AB online. You shouldn't see much disparity between them if your data is solid. If you are seeing big disparity across multiple apps it is definitely a data issue. Its also very important to check your scope for proper tracking. Once you've got this all nailed down there is also a little truing to be done.

Welcome to the addiction, its a blast.

 

[Ffjmoore]

Thanks, I haven't made it back out to the range, it's been over 100 degrees for a while. My list for the range is to confirm zero, and then check the turret tracking. Im pretty sure those are going to be fine and that the real problem is my data was off. What I am starting to understand is if i want to hit things first shoot at long range I need good data. And to get said data I need the appropriate tools, ie. Range finder and a kestrol.