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Confusion on My Ballistics

 
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  #8  
Old 08-07-2005, 12:28 AM
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Re: Confusion on My Ballistics

This is one of the reasons I dont use a 100 yard zero for a referance.

For example: say you are zeroing at 100 yards on a 1" target and your .3" group is inside that circle but its .4" high inside that circle. It may be an acceptable zero for 100 yards, but now you are truly zeroed at 150 yards instead of 100 yards exactly, even though you are hitting small targets at 100 yards.

If you do the math at 90 degrees F. and 800' with slightly lower than standard pressure say .4 inches of mercury and are .4" high at 100 yards you will only need 2.8 MOA to hit at 300 yards. If you do the same math with a true 0.00" zero at 100 yards then it will be 3.27 MOA to hit 300 yards.

Bottom line: I might carry may rifle afield with a 100 yard zero, but when it comes time that I set up for a long shot, I use a verified 300 yard setting as a starting point.

Hope that helps
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Old 08-07-2005, 07:47 AM
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Re: Confusion on My Ballistics

Chris, I had it out yesterday taking measurements on that load. Five shot group avg was 2934, with an extreme spread of 9 fps and standard deviation around 4.
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Old 08-07-2005, 07:51 AM
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Re: Confusion on My Ballistics

Not to start an arguement, but if you punch in different values for scope height it will change very little. Craig and I have already been over that.
That is a good point about having a true 100 yard zero. Zero means zero, not 1/4" high.....it would definitely change things further out.
I imagine his velocity is higher than what he thinks and the BC is too- Sierra tends to be conservative where most other bullet makers exaggerate their BS.
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  #11  
Old 08-07-2005, 08:02 AM
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Re: Confusion on My Ballistics

JBM, the program I use only has inputs for altitude and temp. However, I did run the numbers on an online program that had those inputs. I got roughly the same numbers that I ran at home. At the very least, this ruled out any issue with the program I am using.
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Old 08-07-2005, 08:09 AM
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Re: Confusion on My Ballistics

BC # or like I said- they are a program- meant to get you on paper- but nothing replaces actual dope....
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  #13  
Old 08-07-2005, 09:38 AM
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Re: Confusion on My Ballistics

Craig,
Bottom line is to simply accept what your rifle and load is doing, get a good set of drops, shoot them so you are confident that they are doing what they are doing, and don't waste time wondering why the 'puter projections are different. The time you have spent wondering about this disparity could have been used to load more ammo [img]/ubbthreads/images/graemlins/smirk.gif[/img] Just be glad that you are not getting more drop than the print-out predicts.

You might try some Hornady A-Max's sometime, I am getting amazing accuracy with them in some of the calibers currently being used. Shoot flatter than the HPBT's I am used to - but then that might make the difference from the 'puter projections even greater [img]/ubbthreads/images/graemlins/smile.gif[/img]
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  #14  
Old 08-07-2005, 10:40 AM
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Re: Confusion on My Ballistics

Chris,
No argument started I just did not know what has all been checked and when I run the numbers on my Sierra infinity program with my current conditions and enter 1.5 scope height I get 3.45 MOA at 300YDS.
But then when I enter a scope height of 2.1 which is the height of the scope on my .260 I come up with only needing 3.06 MOA at 300yds. So no, it would not cause all of the error. just throwin' out possabilities.I have had very good results with this program(if I enter all the variables as precise as possable) but yes, there is no substitute for real world drop chart. But the program has proven to be a real time saver for making real world drop charts.
FWIW,
308nate
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