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Can't get ballistic calculations to agree

 
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  #1  
Old 11-26-2011, 12:56 AM
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Join Date: Mar 2008
Posts: 89
Can't get ballistic calculations to agree

Here is the problem: Actual drops recorded are as follows.
1200 yards 8.3 mils
1057 yards 6.4 mils
496 yards 1.6 mils

I must enter numbers like MV 3380 and a BC of .8 with A DK of .445 for a ballistic program to agree with the actual drops.

I have tried this three times and the results are the same. I verify my zero (100 yards) dial 8.3 mills for 1200 yards and get a direct hit dial 6.4 mills for 1057 then dial 1.6 for 496 yards then reconfirm my zero again.

Here is the set-up 7mm WSM 27Ē brux barrel Defiance long action and Nightforce nsx 5.5X22X56 scope mounted 2.7Ē high. I have checked the velocity with 2 cronos. And am getting 3034FPS @ 72 degrees 29.99Ē and 60 percent humidity. Iím shooting the Berger 180 hybrid VLD with a BC of .674 according to Bryan Litzís book. I have calibrated the scope and it's actually .1 mills per click.

Why canít I get my ballistic program to get even close with the above numbers?
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  #2  
Old 11-26-2011, 01:21 AM
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Join Date: Apr 2010
Location: NW Mt.
Posts: 600
Re: Can't get ballistic calculations to agree

Do you have your zero info entered in? Are you using zero info in weather?You appear to be using corrected baro not actual. Do you have the program set right for it? What is the
wind you are shooting in? What program are you running? A lot you aren't telling us.
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Old 11-26-2011, 08:30 AM
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Join Date: Mar 2008
Posts: 89
Re: Can't get ballistic calculations to agree

Iím using Field Firing Solutions and I have checked and rechecked my settings (that is not to say Iím still not making a mistake. I am very familiar with this program and have gotten dozens of other guns/loads to work great without a problem. I take all actual atmospheric data with a Kestrel 4500 and enter it into the program as well as keep records on each shot while trying to develop a drop chart . Can you input the numbers I have into another program and come up with a reasonable solution.
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Old 11-26-2011, 09:42 AM
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Join Date: May 2011
Location: Gillette, Wy
Posts: 83
Re: Can't get ballistic calculations to agree

Lisa,

Have you tried using density altitude instead of entering all the other data?
Your kestrel has that feature. Using DA has helped me more than once.

Altitude here is about 4600 feet, I've seen the DA at 3500ft on a pre cold front day, to 8700ft on a 90 degree day. Crunch those numbers and you can see things change quickly.
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  #5  
Old 11-26-2011, 10:08 AM
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Join Date: Jan 2003
Location: Texas
Posts: 295
Re: Can't get ballistic calculations to agree

Take a look at the G7 Ballistics calculator. The link is dead in the middle of the menu bar on the forum page. Don't overlook the Trajectory Validation button
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Old 11-26-2011, 10:17 AM
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Re: Can't get ballistic calculations to agree

Quote:
Originally Posted by Mike6158 View Post
Take a look at the G7 Ballistics calculator. The link is dead in the middle of the menu bar on the forum page. Don't overlook the Trajectory Validation button
I can't get the G7 online calculator to come up on my Mac. Do you have to access it through a Windows PC?

I want to compare this program to some of the others I'm running. From what I have been reading and viewing on the videos, I really like the features of this program.
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Old 11-26-2011, 10:27 AM
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Join Date: Jan 2003
Location: Texas
Posts: 295
Re: Can't get ballistic calculations to agree

Quote:
Originally Posted by woolecox View Post
I can't get the G7 online calculator to come up on my Mac. Do you have to access it through a Windows PC?

I want to compare this program to some of the others I'm running. From what I have been reading and viewing on the videos, I really like the features of this program.

I have a Mac Pro sitting to the left of my PC (I use it mostly for photo and video editing). I switched to the Mac and the G7 link worked fine. I had to log in but I expected that. I also open it on my PC
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