Advanced Marksmanship Effects of High Altitude on Shooting

[earthquake]

Does there exist any literature on the effects of high altitude shooting that I could get a hold of? Originally from Ohio, I have since moved to Colorado and live at 9,000' above sea-level. I am curious about the effects of altitude on bullet flight (ballistics) due to decreased air resistance, increased solar radiation, decreased humidity etc.

Also, I was wondering if there is any effect on the combustion of the powder and the expansion of gases due to a decrease in atmospheric pressure where I shoot, vs. where I used to, about only 700' above sea-level. I am trying to figure out if I would need to adjust my loads accordingly, or if the effects are too negligible to worry about.

Thanks if anyone can point me in the right direction.

 

[TBass]

Re: Effects of High Altitude on Shooting

A good balistics program will help you with the change in altitude; however, here is a link to a free online program that will allow you to mess around and see some of the effects.

http://www.jbmballistics.com/~jbm/cgi-bin/jbmtraj-5.0.cgi

With respects to the 2nd half of your question, I am not sure

 

[Lindy]

Re: Effects of High Altitude on Shooting

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Also, I was wondering if there is any effect on the combustion of the powder and the expansion of gases due to a decrease in atmospheric pressure where I shoot, vs. where I used to, about only 700' above sea-level.</div></div>

No effect. Considering that chamber pressures are in the vicinity of 50,000 pounds, ambient pressures have no effect.

Muzzle velocity is affected by temperature, depending on the powder and primer used, but the only way to know how much is to shoot over a chronograph at different temperatures.

JBM ballistics, already cited, will help you with air density.

 

[Greg Langelius *]

Re: Effects of High Altitude on Shooting

Mainly, above 6000ft ASL, my vision narrows and sometimes, there are spots...

 

[spaniel]

Re: Effects of High Altitude on Shooting

I went through an extensive exercise last year to make a drop chart for 8000ft for my rifle sighted in at 300ft and 80 degress. Once I got done accounting for altitude/air pressure, temp effects (powder), I found that the effects counter-acted each other and I didn't even bother using them to adjust my drop chart until beyond 700 yards.

I test-fired when I got to altitude, in cooler fall conditions, and was right on. Of course if you have a powder of greater temp sensitivity YMMV.

 

[Lindy]

Re: Effects of High Altitude on Shooting

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...I didn't even bother using them to adjust my drop chart until beyond 700 yards.</div></div>

As a good rule of thumb, I use my standard sea-level dope out to 600 yards under all conditions.

However, it's an excellent exercise to use a ballistic program to see where atmospheric conditions start to affect dope for a particular size target.

 

[psinclair]

Re: Effects of High Altitude on Shooting

Lindy...+1

 

[Sig685]

Re: Effects of High Altitude on Shooting

Muzzle velocity is affected only by the powder charge and the length of the barrel, for the same bullet. Temperature may affect the powder itself but it requires a lot one way or the other.

I would suggest you read up on "density altitude" and relate it to your original location and your new location and then make the adjustments as required.

 

[Nocalphoenix]

Re: Effects of High Altitude on Shooting

I got all worked up over it since my base zero is about 10ft above sea level and I hunt at 6500-7500 feet. Running a .270 (110ttsx at 3400fps) and figuring weather from 40degrees to 100 and elevations from 0-8000 feet it was less than expected.

The worst drop at 600yards was 9.4moa at 1000feet and 50degrees. The flatest was 8.2moa at 8000ft and 90degrees. Long story short it looks ugly at 1000 but at most hunting ranges it is not going to matter and it took an extreme elevation and weather changes to make a difference.