Author Topic: Developing Long Range G7 Spreadsheet  (Read 3637 times)

jrmy_1

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Developing Long Range G7 Spreadsheet
« on: January 17, 2011, 12:17:19 AM »
Hi All,

Brand new to the forum and I love the add-in!!!

Anyway, I have been wanting to develop a spreadsheet based ballistic calculator utilizing the G7 model so I can install on my blackberry.  I want something slightly different in that I want a calculator that I can input rifle zero'ing variables on one sheet and then make a second sheet where I can use the muzzle angle versus line of sight data to develop a new ballistic chart at other conditions, ambient conditions, latitude, azimuth, etc.  I was unable to find any inputs on coriolis effect and spin drift.  Is there any way I can add these into the existing add-in?  Also, any recommendations on how to setup the second spreadsheet based on using muzzle angles calculated from the first spreadsheet.

I want to do this because I'm interested in testing how much additional variance might be attributed to other unknowns and because it's simply something cool to do instead of watch TV.  I would like to be able to sight in my rifle near Houston and go to Wyoming, Michigan, Canada, etc. and estimate where my rifle will hit at different lats, azimuths, etc.  I would also like to have this tested in case I go on a hunt and I can't re-zero my rifle, which really hasn't been the case but still good to know if it can be done and what kind of error I can expect.

Thanks for the great forum!!!
J

admin

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Re: Developing Long Range G7 Spreadsheet
« Reply #1 on: January 17, 2011, 08:40:45 AM »
Welcome, in principle you want a fire control system for a hunting rifle. For target shooters BfX does the job, mostly because the elevations are never in excess of 15 degrees and we are allowed to sight in.
In some  hunting situations (which do not exist in our almost flat Netherlands) you have to shoot up/downhill and the elevations are such that BfX becomes too inaccurate. Furthermore BfX does indeed not include the effects of spin drift and the Coriolis force. They would complicate the BfX-interface and I found  their practical influence, compared to those of wind, negligible. I you would, you can add some formulas to Excel and compute their effect. To release software which has all the capabilities you mention is entirely possible, but I will not do that. There are people who shoot something else than paper targets, use other launchers then rifles and who aim at our soldiers in the mountains of Afganistan.

The last time I checked I found that Excel on Windows mobile does not support add-ins. In my experience the use of tables printed on paper (covered with plastic if you like) is much easier than the use of electronic devices during matches.  I simply do not have the ability to think when there is time pressure.

In the spreadsheet GettingStarted with Excel you will learn everything about generating such tables, including the effects of temperature and pressure. I am not sure if I have still included the effects of humidity, since they are so small for rifle bullets. It will also educate on the use of G1 versus G7 drag functions.

Brian Litz sells a pocket calculator that might help you http://www.appliedballisticsllc.com/index_files/Products.htm


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Re: Developing Long Range G7 Spreadsheet
« Reply #2 on: January 17, 2011, 09:44:39 AM »
regarding humidity, I did not capture its effects in BfX_C.

jrmy_1

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Re: Developing Long Range G7 Spreadsheet
« Reply #3 on: January 17, 2011, 07:13:50 PM »
Thanks for the reply, and again for the tool.  I think your work is a great addition to the community.

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Re: Developing Long Range G7 Spreadsheet
« Reply #4 on: January 17, 2011, 10:12:00 PM »
by the way, one of the most commonly ignored issue to achieve a one shot one kill setup is the calibration of the sights. Is the scope according to the specs?

I have a scope - 230 euros - that has a reasonable optical quality, and has an excelent mechanical quality. I see the black dot in the sight and that is good enough for me. Anyhow, the optical quality was good enough to become 1st in the Dutch 2008 300-500-600 yards (yes yards in the Netherlands too!) F-Class championship and third in 2009. In 2010 the beautiful military shooting range was (probably temporary) closed for us  :'(.  Mechanically the scope is very constant in its moa/click and has no hysterises I know of. But instead of being 1/4 moa per click it is 0,21 or so. And that is an issue if you have to depend on calculations (the rifle was zeroed at 100m and I shot a lot at 500m).

I have a workbook illustrating a scope calibration.
« Last Edit: January 17, 2011, 10:16:17 PM by admin »

jrmy_1

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Re: Developing Long Range G7 Spreadsheet
« Reply #5 on: January 19, 2011, 03:54:39 AM »
Yes, mine is the same, about .230 IPHY per click with no hysteresis that I can detect.  I'm currently using a Wotac Optics, 4-14x, but I'm saving for a Viper PST 6-24x FFP as soon as they re-role out the design.  I would like to have a Night Force, but unfortunately I can't justify the cost at this time.