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Can't get Calculator to match Verified Data

jakhamr81

jakhamr81

Full Member
Full Member
Minuteman
Aug 12, 2009
1,579
32
FT Smith, Ar
#1
I had a chance to shoot my SPR out to 1,000 yards today. I good solid data. My shooter app on my phone seemed a bit off, about .3 mils. I figured I could adjust the MV to get it to match. Problem is, I just can't produce the same data on my shooter app or on the JBM calculator. Here's what I have entered:
Sierra .224 77 gr HPBT
BC .362
MV 2795 @ 10 feet
Sight Height 2.45 in (double and triple checked)
Altitude 6,400
Temperature 76
Humidity 60%

I have a good zero, and when I enter this data it is giving me the following corrections:
500- 3.6 mil
600- 4.7 mil
800- 7.3 mil
900- 8.9 mil
1,000- 10.7 mil
However, these are the elevation settings that I verified.
500- 2.4 mil
600- 3.6 mil
800- 6.1 mil
900- 8.3 mil
1,000- 10.5 mil

The only thing I could think of is that the ranges may not have been true. I did not laze them, but it was a fixed range with fixed yard lines, and all of my .308 data produced by the calculator checked out within .1 mil.

Anyone know what I may be entering wrong?
 
#7
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jakhamr81</div><div class="ubbcode-body">I switched to G7, and am getting the same results.

DA was about 8,500, pressure 30.21 </div></div>

that 30.21 is a corrected number. What are you putting in?
 
#8
Re: Can't get Calculator to match Verified Data

I take that back. On JBM I get the same results. On my Shooter App I get results that are more than a mil less of my actual dope with the G7.
 
#10
Re: Can't get Calculator to match Verified Data

Were are you getting your barometric pressure from?

Because that is a corrected pressure and may not be from where you are shooting. 6400ft will not have a pressure of 30.21, so where is that information from.

As well what is your actual MV ?

Seems like you might be winging it a bit and if that is the case .3 is nothing to worry about. Typically you have a .2 variance also have you calibrated your scope that can be the issue also. If you havent calibrated your scope you can't expect it to be any better.
 
#11
Re: Can't get Calculator to match Verified Data

I would have to assume that the pressure most likely came from the airport reporting which is at 5,834; so that may be one issue. 2795 was my average MV when I zeroed. The chrono was ten feet away.

I have an older Kestrel that does not display pressure. So other than buying a new one is there a way to correct this issue?
 
#12
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Were are you getting your barometric pressure from?

Because that is a corrected pressure and may not be from where you are shooting. 6400ft will not have a pressure of 30.21, so where is that information from.

As well what is your actual MV ?

Seems like you might be winging it a bit and if that is the case .3 is nothing to worry about. Typically you have a .2 variance also have you calibrated your scope that can be the issue also. If you havent calibrated your scope you can't expect it to be any better. </div></div>

"Winging it" would be a pretty accurate description. Calibrating the scope could also be another issue, I just got it mounted a month ago. I will put that on the to do list for my next trip to the range.
 
#14
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body">garbage in.....garbage out.....

</div></div>

Only winging it on the data I did not have access to bro.

Thanks for the help fellas.
 
#15
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jakhamr81</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body">garbage in.....garbage out.....

</div></div>

Only winging it on the data I did not have access to bro.

Thanks for the help fellas. </div></div>

Good data will get you good results.
 
#16
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jakhamr81</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body">garbage in.....garbage out.....

</div></div>

Only winging it on the data I did not have access to bro.

Thanks for the help fellas. </div></div>

Good data will get you good results.</div></div>

Touche'
 
#17
Re: Can't get Calculator to match Verified Data

Have you experienced this "offset" previously? Perhaps the range has a slight elevation from the target area towards the shooting area. This could account for the tenth's error you cannot reconcile with the programs.
 
#18
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jakhamr81</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jakhamr81</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body">garbage in.....garbage out.....

</div></div>

Only winging it on the data I did not have access to bro.

Thanks for the help fellas. </div></div>

Good data will get you good results.</div></div>

Touche' </div></div>

Was not trying to hammer you. Was trying to point out that something was not adding up.
 
#23
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">They will never take the place of actually zeroing a rifle to that range. They are meant to get you close enough to make the hit </div></div>

Agreed. i just wanted to use the ballistic prorams to get solutions taht are close, but I always confirm every chance I get.
 
#24
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">They will never take the place of actually zeroing a rifle to that range. They are meant to get you close enough to make the hit</div></div>

I beg to differ. If the program does its job properly, it should match the trajectory exactly, once properly tuned to that gun/optic/ammo.

In fact, at extreme ranges it is the ONLY reasonable method to get a first round on target For example, I hit the plate near dead center, cold bore, no previous shooters, at 1767 yards just last Sunday during the AZPRC match, despite a more than 2000' DA change from my home range. A range card will not get that done, sorry.
 
#25
Re: Can't get Calculator to match Verified Data

A ballistic calc will never beat DOPE, but here is the kicker.

You can collect DOPE all day long everyday and log it but will you ever shoot in those exact conditions again.... No.

Could they be very close yes and this is why DOPE is useful.

A properly setup ballistic calc will give the shooter a great advantage when sending rounds down range. Just as CoryT stated, I have achieved many first round hits in conditions very different from where I normally collect DOPE.

You need the DOPE to make you BC match these numbers in order to ensure you BC is working at its full potential.
 
#26
Re: Can't get Calculator to match Verified Data

Don't take the above to suggest I think a PDA and software is a replacement for range cards. In fact the large majority of shooters can use just one set of KD data and be just fine. Most don't shoot at long enough ranges, often enough, under enough different conditions to see a variance in zeros greater than their ability to hold and call wind.

Something like the FDAC, or a simple set of DA based cards works plenty fine. Very few people actually NEED anything more than that.

Those that do NEED it have no reasonable alternative. When correctly configured, good software is correct within the limits of the shooter/rifle/ammo, no matter the changes in conditions.
 
#27
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CoryT</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">They will never take the place of actually zeroing a rifle to that range. They are meant to get you close enough to make the hit</div></div>

Like I said before it will get you on target. so you can make the hit at long ranges but it won't get you a gead center bulls eye hit.
As far as matching exactly I have yet to see a program (civilian) that will exactly match no matter how percise you are with your input

I beg to differ. If the program does its job properly, it should match the trajectory exactly, once properly tuned to that gun/optic/ammo.

In fact, at extreme ranges it is the ONLY reasonable method to get a first round on target For example, I hit the plate near dead center, cold bore, no previous shooters, at 1767 yards just last Sunday during the AZPRC match, despite a more than 2000' DA change from my home range. A range card will not get that done, sorry. </div></div>
 
#28
Re: Can't get Calculator to match Verified Data


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jakhamr81</div><div class="ubbcode-body">I take that back. On JBM I get the same results. On my Shooter App I get results that are more than a mil less of my actual dope with the G7. </div></div>

G7 table with Shooter app almost always matches my actual dope, IF I get the other variables correct. The FDAC is likewise very close and usable for "combat" accuracy. Make sure you have D.A. and velocity correct, and you should be gtg.
 
#29
Re: Can't get Calculator to match Verified Data

Greenron, properly calibrated, Field Firing Solutions and Patagonia Loadbase will generate a solution that is as accurate as the rifle/shooter/ammo.

When you say it won't deliver a dead-center bullseye, you need to define what you mean.

Given the unknowable muzzle velocity of the round you are about to fire, plus the unknown aiming error, physical shooter induced gun movement and unknowable actual wind component at the time of firing, exactly how close do you expect to get to 'dead center' with any shot fired at any appreciable range?

If you zero a rifle at say, 800 yards, then a week later shoot at the same range, how close to you think the sight setting you 'zeroed' the gun with will get you to the center? A change of only 1" in station pressure alone will alter the elevation of a 175gr 308 by .13 mil, or 3". Add on a 10 degree change in temp and it's another .1 mil, or 2.8".

Now your 'zeroed' gun is 5.8" off at 800. I, on the other hand, will have made the .2 mil adjustment. Who will be closer to having a centered group?

It's really the other way around. Dope cards are 'close enough', the computer is precise. Many people simply will not calibrate the system correctly to start with, then blame the computer for giving them a wrong answer.

I no longer keep a log book, nor do I create a dope sheet from range firing sessions. I calibrate the computer to the gun/ammo/optic, which typically takes about 20 to 40 rounds and that's it, I can take that gun anywhere on the planet and shoot it to the limits of the system.

Certainly I'll print out DA based charts as a backup, after all, it's a electronic device and subject to failure. But those charts are just that, a backup, like reticle ranging is a backup to the LRF.

I still teach by using actual firing sessions to generate a drop chart, because it's a basic skill which can be used in the absence of anything other than the rifle, ammo and targets. Everyone should know how to do that way, but that's no longer the smart, fast and precise way to get it done.
 
#30
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CoryT</div><div class="ubbcode-body">...properly calibrated, Field Firing Solutions and Patagonia Loadbase will generate a solution that is as accurate as the rifle/shooter/ammo.</div></div>
I state the same for KAC Bullet Flight - field-tested.

<span style="font-style: italic">Based on Lowlight's experience, I didn't trust the Hidden BC. So before leaving for the shoot I manually entered banded G7 BC from Bryan Litz book for the bullets I was going to use (3 profiles). Those few minutes spent on creating the correct profiles paid off very nicely.</span>
 
#31
Re: Can't get Calculator to match Verified Data

Found this. Some good info here. This my help some of you guys understand how to set up your rifle. This is kind of how I do it with Bulletflight and my Kestrel.


<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/mtMmqvfH1po&feature=youtube_gdata_player "></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/mtMmqvfH1po&feature=youtube_gdata_player " type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>
 
#32
Re: Can't get Calculator to match Verified Data


I use bulletflight. I have chronograph my loads enter all the data from kestler into the app and still off. at 200 yards for a 308 168 @2827 fps it says 6 clicks I set it at 4 clicks
at 300 it show 15 clicks I use 17 clicks
I dont think I am doing anything wrong

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CoryT</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">They will never take the place of actually zeroing a rifle to that range. They are meant to get you close enough to make the hit</div></div>

I beg to differ. If the program does its job properly, it should match the trajectory exactly, once properly tuned to that gun/optic/ammo.

In fact, at extreme ranges it is the ONLY reasonable method to get a first round on target For example, I hit the plate near dead center, cold bore, no previous shooters, at 1767 yards just last Sunday during the AZPRC match, despite a more than 2000' DA change from my home range. A range card will not get that done, sorry. </div></div>
 
#33
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">
I use bulletflight. I have chronograph my loads enter all the data from kestler into the app and still off. at 200 yards for a 308 168 @2827 fps it says 6 clicks I set it at 4 clicks
at 300 it show 15 clicks I use 17 clicks
I dont think I am doing anything wrong

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CoryT</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">They will never take the place of actually zeroing a rifle to that range. They are meant to get you close enough to make the hit</div></div>

I beg to differ. If the program does its job properly, it should match the trajectory exactly, once properly tuned to that gun/optic/ammo.

In fact, at extreme ranges it is the ONLY reasonable method to get a first round on target For example, I hit the plate near dead center, cold bore, no previous shooters, at 1767 yards just last Sunday during the AZPRC match, despite a more than 2000' DA change from my home range. A range card will not get that done, sorry. </div></div></div></div>


I would bet something is off... Bulletflight is very accurate, you have to know what all the variables are, how correct your chronograph is, is your scope correct and calibrated, there is more to using a ballistic calculator then just dropping in the data you collect, you have to understand the data. How is your Kestrel set up, etc.

Especially at 200 yards, nothing should be very far off at that close distance most issues of environmental conditions don't have enough time to act on the bullet to cause a big deviation.
 
#34
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">I use bulletflight. I have chronograph my loads enter all the data from kestler into the app and still off. at 200 yards for a 308 168 @2827 fps it says 6 clicks I set it at 4 clicks
at 300 it show 15 clicks I use 17 clicks
I dont think I am doing anything wrong</div></div>
What do you use for BC? I use banded G7 BC form Bryan's book, manually putting them in for each new profile.
 
#35
Re: Can't get Calculator to match Verified Data

Just spoke to them at Bulletflight and they said the same thing as I have said. It is meant to get you on target but you will need to fine tune your scope at the different ranges
 
#36
Re: Can't get Calculator to match Verified Data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greenron15</div><div class="ubbcode-body">

I dont think I am doing anything wrong

</div></div>

Well of course you don't, otherwise you would do something different. Sadly this is no guarantee that you are not doing something wrong. Or perhaps I am wrong
 
#37
Re: Can't get Calculator to match Verified Data

When they say fine tune, that for long ranges where the lack of a turret calibration comes into play. At 200 yards, no reputable ballistic program is going to differ by 1/8 of a minute, and they will all be correct FOR THE DATA ENTERED!

For example, if you enter station pressure, as read off the Kestrel, but the referance altitude is set to 5000 feet, you have a problem. Looks fine to the casual observer, but it's not generating a solution for the actual conditions.

Bottom line, there is no way that Bullet Flight is off by .5 MOA at 200 yards if the correct info is being fed to it.
 
#38
Re: Can't get Calculator to match Verified Data

Ok, so I'm pretty sure that not having the exact muzzle velocity and true pressure of the exact spot that I was in will give me between a .3 and 1.1 mil difference between my Shooter App and the actual data I was shooting.

So other than my scope not tracking true, what could be the problem? I am using . BC on my Black Hills .77 grain MK262 ammo. The range should be true as I was shooting on a KD range.
 
#39
Re: Can't get Calculator to match Verified Data

I would agree that bullet flight should no be off by .5 moa at 200. The problem I am having is I have two profiles to get accurate data. I have a profile that is out to 600 and a profile greater then 600. Data is accurate on both to actual dope and conditions. My search which lead me to here is what am I doing that requires the program to have two profiles?
 
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