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Range card format Help

 
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  #1  
Old 03-25-2013, 07:10 PM
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Join Date: Nov 2011
Posts: 53
Range card format Help

what all is everyone putting on their range cards? Ive been trying to decide how i want to make my range cards efficiently and im struggling. I will be doing my adjustment it MOA. I plan on having:

vertical adjustment
horizontal adjustment- just 5mph then ill multiply for various conditions
potentially angles for every range @ 15, 30, and 45 degrees
and i would like to make my series of cards with variable temp and pressures
im just not sure if its safe to substitute "elevations" for pressures

But i guess im hung up on how people are dealing with atmospheric pressure changes. I feel like a kesterl is the best solution to this problem, but since i dont have one whats my best game plan? I see the ballistic calculator on LRH mag uses various elevations if you print off their set of range cards, and so does JBM. I dont understand atmospheric presssure very well. The higher in elevation the lower the pressure correct? is it safe to base your range cards on average elevations instead of actual pressures? does the pressure stay the same at the same elevation at different seasons? a

and finally how many people are accounting for spin drift on their cards?

thanks for the advice!
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  #2  
Old 03-25-2013, 07:52 PM
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Join Date: Feb 2013
Location: Central MT
Posts: 579
Re: Range card format Help

300 RUM DA1000, 10MPH


Range ELV Wind SD
etc etc etc etc
1000 18.5 4.5 L2


Here is an example of the range cards I use. I know you said you don't have a weather station but they are sure handy with computing the density altitude, they take out most of the guess work. I will have a card for every 1000ft of Density Altitude and take three or four with me for the day depending on anticipated weather changes. Ranges every 10 yards starting around 400 yards up to the maximum range. For COS(X) I will use a calculator if needed. Very simple to use.
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  #3  
Old 03-25-2013, 09:50 PM
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Re: Range card format Help

pressures can vary quite a bit at the same elevation throughout the year right?
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  #4  
Old 03-25-2013, 10:48 PM
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Location: Central MT
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Re: Range card format Help

Quote:
Originally Posted by gphil View Post
pressures can vary quite a bit at the same elevation throughout the year right?
I have seen DA change as much as 4000 feet in the same day, at roughly the same elevation. Most change was due to a drastic change in temperature from early morning temps near 0 F to a mid afternoon high in the upper 60's.
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  #5  
Old 03-25-2013, 10:59 PM
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Join Date: Nov 2011
Posts: 53
Re: Range card format Help

thats interesting, I thought that they could change quite a bit, Im glad i checked.

what does DA stand for?

when people say elevation they are substituting that for an average pressure value correct?
for example on here if you print off a series of range cards it gives you various elevations and temps. The elevations are based on the average pressures at the elevations provided arent they?
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  #6  
Old 03-25-2013, 11:15 PM
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Join Date: Feb 2013
Location: Central MT
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Re: Range card format Help

Density altitude is the altitude of the standard atmosphere (sea level, 29.92 in/Hg, 59F) at which the air density would be equal to the actual air density at the place of observation. If you are standing at sea level with the standards described above and the temperature changes to a higher temperature, lets say 90F, your density altitude would then be greater than sea level or 0 ft.

I guess you could say DA is the altitude the bullet "thinks" it's flying thru using the standard as reference.
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  #7  
Old 03-25-2013, 11:45 PM
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Re: Range card format Help

alright thanks that helps me alot. so really you almost have to have something to read your pressure and temp to be as accurate as possible.

So when your inputting data into your PDA or phone in the field as long as you know your pressure you dont need to input your elevation do you ?

DO you correct for spindrift?
which kestrel do you use?

I apologize for the slew of questions this whole correction thing has had be balled up. Ive been playing around a little with shooting jugs and i can make hits at 500 and 600 fairly common but 700 is a totally different ball game it seems. Im thinking part of it is due to not having accurate correction data.
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