Altitude

[beep_gun]

Does it matter? I'm gonna shoot at 7k ft zero'd at sea level.

[joelogic]

Yes, less dense air, less air to consume, temp. Enter your data into a ballistic calculator for details.

But wont matter at short distances.

[beep_gun]

Is there an app for that?

[ExtremeX]

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.

[Divernhunter]

You will shoot higher. Also it will take more powder to show high pressure signs.

[GeoffLinder]

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

[San_Diego_Shooter]

Yes. Watch this: https://www.youtube.com/watch?v=socvpNPi6DA

[FMJBT]

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.

[beep_gun]

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

[Don@Tahoe]

Interesting, I live at 7,000, never thought about altitude affecting my loads, Duh!

[Bill Steele]

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.

[Diabolus]

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.

[Cheap Shot]

App for that...

STELOK for android and I believe apple also.

[GeoffLinder]

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.