Velocity and Altitude question

Marble

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Joined
Jul 19, 2012
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362
Location
Shasta County
I live 500' above sea level and hunt at 9000-11500 feet. I know ballistics change with altitude, but I'm wondering if velocity does too. If I recall correctly, if I'm shooting 3280 at 500' elevation, at 11000 or so, the velocity should be higher. I guess the sure way to know is shoot the gun through my chrony at somewhere close to that altitude, but I can't do that until I go back in October.

Or, do I put the parameters into the ballistics calculators and do they do the math for me?
 
Velocity change in the barrel due to elevation is not a factor. A chrony 15 Ft away will probably be well within your ES to and not a factor.

If you use an app like Shooter, it calculates the altitude change for you based on the altitude/temp/pressure where you sighted in at.


It is a very good idea to actually do some practice shots and verify everything at the altitude you will be hunting at anyway IMHO.
 
It's an INTERNAL ballistic factor and wouldn't be accounted for in any EXTERNAL ballistic math.
I know it can affect tune. I don't know about muzzle velocity.
 
Velocity change in the barrel due to elevation is not a factor. A chrony 15 Ft away will probably be well within your ES to and not a factor.

If you use an app like Shooter, it calculates the altitude change for you based on the altitude/temp/pressure where you sighted in at.


It is a very good idea to actually do some practice shots and verify everything at the altitude you will be hunting at anyway IMHO.

Thanks for the info.

I always shoot my guns when I arrive and reconfirm zero.

My main reason for asking is I was going to have some turrets made with the drop built in. I'm just trying to make it the best I can before I go ahead with it.
 
Well, different air density being pushed down a bore could affect the pressure curve a bit, affecting your accuracy. But there are a lot of variables to internal ballistics that could ultimately sum to actual muzzle velocity change -or not.
 
You are not likely to see a big change, if any in muzzle velocity, but it's still advisable to re-zero when changing locations of different altitudes. The difference in the altitude/air density, will produce a lower resistance on the bullet, producing higher retained velocities at longer ranges, thus requiring a lower elevation correction at those longer ranges. a ballistic program , like Shooter will provide the corrections when the air density/altitude info is inputed for the higher elevation.
 
I figured it wouldn't make too much of a difference. I always confirm zero when I travel. So I will get my new turret and give it a try. I'm going to get back there a few days earlier than normal this year anyways so maybe I'll climb up a mountain and find something close to 800 yards out and give it a few shots to confirm.
 
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