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ballistic software question

 
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  #1  
Old 03-20-2011, 09:15 PM
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Location: Sonoma County, CA
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ballistic software question

I have been looking into ballistic software programs. This may be a VERY stupid question, but I dont know the answer and you guys have always answered my stupid questions in the past. If I zero my rifle at 250 yards @ 0' elevation. Then an hour later I drive up a mountain to 3000' elevation. I punch in the distance to a steel gong I have (980 yards), punch in the wind, elevation, pressures and so forth. Will my rifle being sighted in @ 0' elevation screw up my POI at 3000' elevation? what if it were 6000' elevation?

The reason I ask, where I will be hunting black bears this year, the elevation ranges from 1000' to 4500'. I was just curious how you guys deal with the different air densities.

Thanks, Nick
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  #2  
Old 03-20-2011, 10:00 PM
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Re: ballistic software question

Nick,

As long as you zero at a short range, like 100 yards, that zero will hold for a very wide range of altitudes and atmospheric conditions.

However if you zero much further, like 600 yards, then that zero is very subject to the atmospheric conditions that were present when you zeroed.

I always advise 100 yard zeroes. They're just more reliable and simplify things greatly compared to longer range zeroes.

-Bryan
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And: Accuracy and Precision for Long Range Shooting

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  #3  
Old 03-20-2011, 10:15 PM
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Re: ballistic software question

Bryan,

I'm not going to argue with you, but perhaps you could clarify for me as well. It seems that the function for entering these values into a program addresses this very issue. I'm using Shooter for android and it asks for zero conditions. (you worked on this I believe?) Am I assuming to much in thinking that it takes my base values into consideration when delivering a shooting solution at higher elevations?
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  #4  
Old 03-20-2011, 10:45 PM
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Re: ballistic software question

texan,

You're correct. In a program that allows you to define your zero conditions, if you enter those conditions properly, then your trajectory predictions will be good in all conditions.

This is a feature of the program that "allows you to do it the hard way", in my opinion.

For one thing, not all programs have that feature, so if you're using one of those programs, you simply can't use a long range zero reliably.

Second, if you used a 100 yard zero, you could simplify your process by totally skipping the steps of measuring and entering your zero conditions.

Plus, think about this. If you use a 100 yard zero, you can 'verify' and refine your zero everytime you shoot at 100 yards, regardless of the conditions. But if you're using a 600 yard zero that's subject to the conditions which you have to store with that zero, then your zero will only ever be tied to one shooting 'session'.

Again, you're correct that it's possible with some tools to overcome the challenges of long range zeroes, but it is my opinion that shooters lives would be less complicated in most cases by using 100 yard zeroes.

An exception might be a shooter who expects 'fast shot' opportunities at relatively short range, and wants to zero high at 100 yards for a ~200-250 yard 'point blank' trajectory on a given size vital zone. But that scenario is outside the scope of this 'Long Range' Forum.

Take care,
-Bryan
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And: Accuracy and Precision for Long Range Shooting

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  #5  
Old 03-20-2011, 10:55 PM
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Re: ballistic software question

Quote:
Originally Posted by bsl135 View Post
An exception might be a shooter who expects 'fast shot' opportunities at relatively short range, and wants to zero high at 100 yards for a ~200-250 yard 'point blank' trajectory on a given size vital zone.
Bryan,
Thanks for the input. I completely understand what you are saying. Makes alot of sense. I put my .300WM together so it could be a point and shoot out to 300 yards, but is also capable of reaching out and making an accurate shot to xxxx yards. So in other words, Iam not entirely sure what I am going to do now. I would like to have a 250 yard zero but that may not be a wise decision.

I plugged in my info into a ballistic calculator and got this for 700' elevation and 6000' elevation:

250yd Zero @ 700' Elevation:

50yds - .8"
100yds - 2.3"
150yds - 2.7"
200yds - 2.0"
250yds - 0"
300yds - -3.3"

250yd Zero @ 6000' Elevation:

50yds - .8"
100yds - 2.3"
150yds - 2.7"
200yds - 1.9"
250yds - 0"

As you can see, at 6000' elevation my trajectory changed at 200yds. It went from +2.0 to +1.9. So if I punched into a ballistic software that I am at 6000' elevation, a perfect 1000 yard target and my rifle zero is at 250 yards. It seems as if that would work? not sure......

Last edited by Nikolakangrga; 03-20-2011 at 11:14 PM.
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  #6  
Old 03-20-2011, 11:09 PM
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Re: ballistic software question

Nik,

One possibility to consider is to establish your 100 yard zero (set your scope turrets to 'zero' there).

Then, figure out how many clicks up gives you the 250 yard zero and apply that adjustment when you're expecting a fast shot at close range. This may compromise accuracy slightly for the short range 'point and shoot' scenario (because the 250 yard zero will be slightly affected by conditions), but it will preserve the accuracy for longer range shots which is where you need it more anyway.

Just a suggestion.

Good luck with whatever you decide.

-Bryan
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Bryan Litz
Ballistician

Author of: Applied Ballistics for Long Range Shooting
And: Accuracy and Precision for Long Range Shooting

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  #7  
Old 03-20-2011, 11:29 PM
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Join Date: May 2009
Location: Sonoma County, CA
Posts: 154
Re: ballistic software question

Bryan,
Thanks for the input. I completely understand what you are saying. Makes alot of sense. I put my .300WM together so it could be a point and shoot out to 300 yards, but is also capable of reaching out and making an accurate shot to xxxx yards. So in other words, Iam not entirely sure what I am going to do now. I would like to have a 250 yard zero but that may not be a wise decision.

I plugged in my info into a ballistic calculator and got this for 700' elevation and 6000' elevation:

250yd Zero @ 700' Elevation:

50yds - .8"
100yds - 2.3"
150yds - 2.7"
200yds - 2.0"
250yds - 0"
300yds - -3.3"

250yd Zero @ 6000' Elevation:

50yds - .8"
100yds - 2.3"
150yds - 2.7"
200yds - 1.9"
250yds - 0"

As you can see, at 6000' elevation my trajectory changed at 200yds. It went from +2.0 to +1.9. So if I punched into a ballistic software that I am at 6000' elevation, a perfect 1000 yard target and my rifle zero is at 250 yards. It seems as if that would work? not sure......
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