How Air Density Affects Long-Range Shooting

If your home range is in high in the mountains, you're going to find ammo behaves a lot differently at lower altitudes; understanding the concept of density altitude will give you a leg up

How Air Density Affects Long-Range Shooting

Air is comprised of billions of molecules the bullet must push aside on its way to the target. Each molecule the bullet hits robs it of a tiny fraction of its energy, and thus the bullet slows. So if the air is less dense--fewer molecules occupying a specific volume of space--a bullet does not experience as much drag force against it and so slows at a lower rate and is traveling faster than normally expected when it arrives at the target.

This shortens its time of flight, meaning gravity does not have as much time to pull it downward and thus our shot goes higher than we would see in a denser air condition. Therefore, when it comes to long-range competition, it's important to have an understanding of how changes in these conditions will influence your trajectories as the weather changes or as you travel to different areas of the country.

Atmospheric conditions--barometric pressure, altitude, temperature and humidity--influence air density. Storm fronts, cold fronts, warm fronts, temperature changes and so on mean the atmosphere changes continually. This makes it impossible to derive a set of equations that positively states what the density, pressure or temperature will be at a given altitude, yet we need a reasonably accurate estimate of these things.

Because this estimate is important for aviation and weather forecasting, the U.S. Army created a standard atmosphere model Standard Metro model, which it used until the early 1960s and is still employed by the shooting industry to this day because of the wealth of data it generated in its 50 or so years of use.


Pilots have need of this same information as well, since air density affects aircraft performance. Rather than have equations to calculate the actual air density, they have long used a simple graphical chart that gives them a value they call "density altitude."


This is the altitude in the standard atmospheric model at which point the air has the same density as the air that we are flying or shooting in. Put very simply, density altitude is the elevation at which the bullet thinks it's flying.

We now have only one variable to account for all other parameters we normally have to factor in. Let's suppose a shooter wants to sit down in front of his laptop and compute ballistic charts for every situation he could reasonably expect to find himself in--from shooting in shooting in warm humid weather at sea level in Louisiana to freezing cold in the Rockies at 7,000 feet. How many tables would it take to encapsulate all of this data?

We don't need to make a chart for every single degree of temperature change or every single foot of altitude and every percentage point of humidity, but let's say every 10 degrees from 0 to 100 degrees and every 1,000 feet from sea level to 7,000 feet, and every 25 percent change in humidity. That alone would require 440 charts.

If we instead use the concept of density altitude, we will make a ballistic table for every 1,000 feet of density altitude from sea level to, say, 8,000 feet, and put that data in columns on one single sheet. We have just reduced several hundred charts to a single page, and our information is functionally just as accurate.


That simplification saves a huge amount of effort and time. All we need to know then is our density altitude. How do we figure that? Hand-held electronic units such as the Kestrel 4000 are recommended for extreme ease and precision, and you can find density altitude calculators on the internet. I've also developed a new version of the DTAC reticle that takes this atmospheric information into account.

This information is invaluable to me in my travels from my home in Texas to Camp Perry, Ohio, or to Raton, New Mexico. Both these locations produce substantially different behaviors from my ammunition. Likewise, it's essential to be able to estimate and interpolate the atmospheric condition effects at each of those places under different circumstances once I'm there.

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

See More Recommendations

Popular Videos

Springfield Armory Saint Victor

Springfield Armory Saint Victor

The SAINT' Victor Rifle delivers a lightweight and agile rifle solution while maintaining effectiveness at extended engagement distances.

Mossberg Patriot Predator 6.5 PRC Revew

Mossberg Patriot Predator 6.5 PRC Revew

Mossberg Patriot Predator 6.5 PRC Revew

Ruger Launches New American Rifle Predator in 6.5 Grendel

Ruger Launches New American Rifle Predator in 6.5 Grendel

OSG's Lynn Burkhead and Ruger's Matt WIlson kick off SHOT Show 2018 by taking a look at the Ruger Predator.

All About .300 Blackout

All About .300 Blackout

The .300 Blackout is here to stay, and we take some time to look at new technology surrounding this cartridge. Next, we pit subsonic rivals against each other before stretching the legs of this CQB round out to 600 yards from a short 9-inch barrel.

Trending Articles

Nosler pairs its M48 action with a new Proof Research carbon-fiber barrel for a high-tech long-range rifle you can actually carry: the Nosler Model 48 Long Range Carbon. Reviews

Nosler Model 48 Long Range Carbon Review

Layne Simpson - March 13, 2019

Nosler pairs its M48 action with a new Proof Research carbon-fiber barrel for a high-tech...

Winchester Repeating Arms releases the new autoloading Wildcat 22 LR rimfire rifle. Rimfire

Winchester Releases Wildcat 22 LR Rimfire Rifle

Rifle Shooter Digital Staff - April 11, 2019

Winchester Repeating Arms releases the new autoloading Wildcat 22 LR rimfire rifle.

Thompson/Center and S&W's Performance Center team up to build an entry-level long-range chassis rifle. Reviews

Performance Center-Thompson/Center LRR Review

Alfredo Rico - April 09, 2019

Thompson/Center and S&W's Performance Center team up to build an entry-level long-range...

Smith & Wesson's M&P15 SPORT II OR rifle with Crimson Trace CTS-103 optic will be on display at the Smith & Wesson Booth at the 2019 NRA Show. MSR

M&P15 SPORT II Rifle Available with CTS-103 Optic

Rifle Shooter Digital Staff - April 23, 2019

Smith & Wesson's M&P15 SPORT II OR rifle with Crimson Trace CTS-103 optic will be on display...

See More Trending Articles

More Long Range

Here are six important considerations to help you make the long-range shot of your life Long Range

6 Steps to Improve Long-Range Shooting Accuracy

Brad Fitzpatrick - June 16, 2015

Here are six important considerations to help you make the long-range shot of your life

We all have our definitions of what constitutes Long Range

Long Range Shooting

Craig Boddington - July 21, 2011

We all have our definitions of what constitutes "long range shooting," and we all have our...

Sniper competitions have been around for a long time, but with the growing interest in long-range precision shooting, the matches are moving beyond just military and law enforcement personnel. Long Range

Evolving Sniper Competitions

David Tubb - February 22, 2011

Sniper competitions have been around for a long time, but with the growing interest in...

A little concept called density altitude has a big effect at long range. Long Range

How Air Density Affects Long-Range Shooting

David Tubb - September 23, 2010

A little concept called density altitude has a big effect at long range.

See More Long Range

GET THE MAGAZINE Subscribe & Save

Digital Now Included!

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE

GET THE NEWSLETTER Join the List and Never Miss a Thing.