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Ammo and Reloading Factory Ammunition, Reloading, Components, Load Data and more.

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  #1  
Old 01-29-2013, 10:11 PM
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Default Altitude

Does it matter? I'm gonna shoot at 7k ft zero'd at sea level.
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Old 01-29-2013, 10:14 PM
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Yes, less dense air, less air to consume, temp. Enter your data into a ballistic calculator for details.

But wont matter at short distances.
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Old 01-29-2013, 10:40 PM
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Is there an app for that?
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Old 01-29-2013, 11:13 PM
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Quote:
Originally Posted by beep_gun View Post
Is there an app for that?
Yup,... various apps on the market for that.

I use Ballistic AE for iOS

http://ballistic.zdziarski.com/

Excellent application too, great learning tool as well.
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  #5  
Old 01-30-2013, 7:44 PM
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You will shoot higher. Also it will take more powder to show high pressure signs.
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  #6  
Old 01-30-2013, 8:47 PM
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Lower air density equals less drag, therefore velocity drop is less across distance and therefore bullet gets there faster which equals less drop. Time to target equals drop because gravity is the constant in play here.

Humidity will effect this too. Denser air always = more drag/drop across specific distance.

Basic calculators will not always support these functions. I like RSI Shooting Lab: http://www.shootingsoftware.com/ballistics.htm
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  #7  
Old 01-30-2013, 8:52 PM
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Yes. Watch this: https://www.youtube.com/watch?v=socvpNPi6DA
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Old 01-30-2013, 9:22 PM
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Altitude makes a huge difference. I have a friend in new Mexico that routinely shoots 168 Sierras out of a 308 to 1000 yards without much difficulty. He's at 5000+ feet in elevation. Where I shoot out here is just under 1500 feet in elevation, and the same bullet shot under very similar conditions with the exception of elevation is a complete turd at 1000 yards. Down here they transition to subsonic at around 800 to 850 yards. After that they just spin end over end and normally group within about 6 to 8 feet at 1000 yards.
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  #9  
Old 01-31-2013, 7:13 PM
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Thanks guys! Good info. Sure makes sense that elevation would effect a bullet. Nice to have facts, reference points and real experience you have presented.



Brian
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  #10  
Old 02-01-2013, 3:51 PM
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Interesting, I live at 7,000, never thought about altitude affecting my loads, Duh!
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Old 02-01-2013, 4:30 PM
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It's all about air density.

1) Altitude - big factor
2) Air Temp (higher temp less dense) - big factor, not as big as Altitude unless temps are at extremes.
3) Humidity (More humid less dense) - small factor, for all intents ignore it.

It has the biggest impact at greater distances.

Pilots think about it a lot, they call it Density Altitude.
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Last edited by Bill Steele; 02-01-2013 at 4:38 PM..
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  #12  
Old 02-01-2013, 6:28 PM
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Quote:
Originally Posted by FMJBT View Post
Altitude makes a huge difference. I have a friend in new Mexico that routinely shoots 168 Sierras out of a 308 to 1000 yards without much difficulty. He's at 5000+ feet in elevation. Where I shoot out here is just under 1500 feet in elevation, and the same bullet shot under very similar conditions with the exception of elevation is a complete turd at 1000 yards. Down here they transition to subsonic at around 800 to 850 yards. After that they just spin end over end and normally group within about 6 to 8 feet at 1000 yards.
That sounds right, needs to go with the 175gr SMK.
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  #13  
Old 02-01-2013, 7:30 PM
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App for that...

STELOK for android and I believe apple also.
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  #14  
Old 02-01-2013, 7:58 PM
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Quote:
Originally Posted by Don@Tahoe View Post
Interesting, I live at 7,000, never thought about altitude affecting my loads, Duh!
As long as you sight in at that altitude and shoot at that altitude you will not see any problems. It's when you sight in and load test at one altitude and then shoot at another that you have to worry.

It takes at least a couple thousand foot difference to have much effect.
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