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Ballistics isn't the math the math?

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Unread 02-12-2012, 12:00 AM
Silver Member
Join Date: Aug 2010
Location: Reno Nevada
Posts: 224
Ballistics isn't the math the math?

Today at the range, shooting @ 960 yds I checked my bullet calcs and hit the gong dead center. After coming home, and looking at 3 different ballistic programs that use all the variables to calc drop, I came up with three different answers, that were as much as 1.5 moa apart.... Isn't the math the math?
I rechecked my solutions all the variables were the same...but the answers seem to start changing at about 600 yds...
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Unread 02-12-2012, 12:53 AM
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Join Date: Oct 2009
Location: Thunder Basin, WY
Posts: 1,788
Re: Ballistics isn't the math the math?

I've noticed the same thing, although not quite that big of a difference.

I've got two versions of the Exbal program, and the PDA version has to have 1/2" HG less pressure to give identical results as the PC version. I read somewhere that it was due to different atmospheric models used. Also, I've got the Sierra software, and it doesn't exactly match the Exbal outputs.

Everything was input exactly the same and Sierra gives 6" more drop at 1000 and 3" more drift.??

Perhaps they use different drag models also.?
Aim small = Miss small

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Unread 02-12-2012, 11:04 PM
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Join Date: Jul 2009
Location: GEORGIA
Posts: 1,237
Re: Ballistics isn't the math the math?

That is why you should shoot your own drop chart with "your" rifle.

This is what I did before I had Vortex make me a custom turret.

Testing new Vortex custom turret. - Georgia Outdoor News Forum

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Unread 02-13-2012, 01:46 AM
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Join Date: Apr 2007
Location: ALASKA
Posts: 504
Re: Ballistics isn't the math the math?

IMHO--I don't have the science to back this up, but it's my conclusion on my personal experiences....that each rifle has a unique BC due to variances in stability and groove/bore signature the rifle's barrel imparts on the bullet. So your results in the field vs the computed by your ballistic solution CAN vary (and very likely will).

Have you "track checked" your rifle scope yet? You may find that more/less elevation is being applied to your reticle than is indicated by your turrent.

A yard stick at 100 yds, with the rifle locked into a vice, and then manipulate the elevation turrent to the 960 yd solution, and see if your scope is applying the assumed solution.

If you hang the yard stick level with a plumb line, you can verify your optic isn't introducing any "windage" into your elevation only solution as well, during this same range session.

Good shooting!
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Unread 02-13-2012, 11:20 AM
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Join Date: Oct 2007
Posts: 1,213
Re: Ballistics isn't the math the math?

I agree....every gun lets em fly different. BUT....I think that the programs should all spit out the same numbers.

I think we should get the government involved to find a solution and fix the problem. Obama's team will ger-R-done!!


Sorry...couldn't resist.
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Unread 02-13-2012, 07:36 PM
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Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: Ballistics isn't the math the math?

You're right. Math is math.

But, there are a number of reasons why different software may give different solutions especially as you extend your distance.

- different assumptions (e.g. atmospheric conditions, scope height, inches or true MOA, corriolis, spin drift)
- rounding error (depending on how the program was written)
- software bugs (there are sometimes bugs in the application, libraries, or even a chipset)
- sloppiness (did the programmer ever think you'd shoot past 1000 yds?)
- stacking error (a little bit here and there adds up at longer ranges)

Similarly, shooting results may deviate from software predictions for a variety of reasons.

-- richard
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Unread 02-13-2012, 08:02 PM
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Join Date: Jul 2005
Posts: 63
Re: Ballistics isn't the math the math?

Different ballistic programs use different mathematical equations to predict the bullet's performance in flight, and even ballistic computers that use the same basic math will likely have been "tweaked" by the software programmer either to improve it, or to make the necessary alterations to avoid infringing intellectual property patents.

So unless a ballistic program licenses and employs identical software the output will be different.

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