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Help: Gun vs.Target - steep shots, barometric adjustments with big elevation change?

 
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  #15  
Old 02-17-2008, 08:26 AM
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Augustus

Use JBM and run a velocity of 3360 fps and a BC of 0.8. Check total drop at 1000 yards for -30 degrees and for +30 degrees.

Augustus, the take away message from the linked post of Shawn Carlock's is that you multiply the cosine times the drop not the distance. And if you have it, that a good PDA ballistics program is even more accurate than the cosine times the drop method.



Pstimac

Consider that the density of air decreases in the uphill direction and that drag on the bullet is decreasing more and more as the bullet flies further uphill thus even though gravity is slowing the bullet down, the air resistance is easing up and letting the bullet keep its speed.

Going downhill, gravity is speeding up the bullet but the air is getting more and more dense the further downhill the bullet goes and slowing the bullet down. Thus in the downhill direction, the greater density is reducing the speed increase by gravity. However, being as the effect of gravity is two to four times greater then the effect of density, the gravity effect is more important than the density. And neither is really important until you get out into the the original distance you specified of 2K.

Now then, it is possible that I have something backwards being as I was trained to work with a pencil, paper and sliderule and working with a computer sketch pad does not come natural to me.
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  #16  
Old 02-17-2008, 10:48 PM
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OK thanks, I use the Atrag2p it works fine so far anound here I dont run into to many steep angle shots but the link was a good read.
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  #17  
Old 03-04-2008, 06:40 PM
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.. found the answer

Got this from exterior ballistics which is home to Sierra's ballistic software:

5.2 Effects of Altitude and Uphill/Downhill Shooting

Sierra's computer program for exterior ballistics calculates precise bullet trajectories at any altitude and for any firing angle, uphill or downhill. The program not only accounts for the altitude of the shooter, but it also calculates the change in drag that occurs as the bullet changes altitude after it leaves the muzzle. With this capability we can see exactly what effects altitude and firing angle have on the trajectory of any bullet.
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  #18  
Old 03-04-2008, 07:21 PM
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You are a good guy to keep digging for your answer. Good work on your part.
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