What is “Density Altitude?"

by
posted on August 8, 2012
bs_2015_fs.jpg (16)

The Background
As more and more hunters and shooters explore the complexities of long range shooting, factors like barometric pressure, altitude, and humidity have all the sudden entered into the shooting equation. At most hunting distances, none of these things matter: range, angle, and wind are the only real external factors that will cause a miss in the first 300 or so yards.

The Question
I recently had a chance to try out a Kestrel 4000 wind meter (available from Sinclair) that provides the shooter with, among other things, a density altitude reading. As if calculating this stuff wasn’t confusing enough, what in the heck is “density altitude”?

The Expert Deferral
We reached out to our friend Paul “The Rocket Scientist,” who is literally a scientist who spent his career working on things like missile guidance systems. He’s also a long-range rifle shooter. His verbatim answer:

Density altitude X is the altitude that, on a day with standard pressure and standard temperature, would have a geographic altitude of X. In hot weather the density altitude is always higher (i.e., less dense) than the geographic altitude (from a topo map or GPS) because the temperature is always hotter than a standard day. Conversely for a cold day. Washington, D.C. at 100F has a density altitude of about 2700 ft even though the geographic altitude (the real altitude of the dirt) is very close to sea level. What really matters to the bullet is the actual density, usually measured in pounds per cubic feet. Sea level standard day (59F) is 0.075lb/cubic foot. But for every combination of pressure, temperature and humidity (ignore for practical purposes) there is a unique density and therefore a unique density altitude.

The Layperson’s Translation (I hope)
Density altitude is the altitude that actually matters in the context of shooting. When calculating a bullet’s path, the density altitude should be used in the equation if it is available.

Latest

Xpert Waterfowl Commermorativemacks Prairie Wings
Xpert Waterfowl Commermorativemacks Prairie Wings

Winchester Ammunition Honors Mack’s Prairie Wings and Marion McCollum

In honor of the 80th anniversary of Mack’s Prairie Wings and its former President and CEO, the late Marion McCollum, Winchester Ammunition has announced a special commemorative Xpert waterfowl ammunition offering available fall 2024.

NRA Files Lawsuit Challenging ATF’s “Engaged in the Business” Rule

The National Rifle Association of America (NRA) has filed a lawsuit challenging the Bureau of Alcohol, Tobacco, Firearms and Explosives’ (ATF) “Engaged in the Business” Final Rule. The ATF’s Final Rule unlawfully redefines when a person is “engaged in the business” of dealing in firearms and therefore required to be federally licensed.

Federal Ammunition Awarded USSOCOM for Mk316

The United States Special Operations Command (USSOCOM) has awarded Federal Ammunition a one-year, $3.6M contract to supply SOCOM with 7.62x51mm rifle ammunition.

Late(r) in Life Hunting

You’re never too old to learn something new.

Recipe: Hunter Slow-Cooker Jambalaya

Creating a flavorful meal from proteins harvested throughout the year is special. A jambalaya made from big game, birds, home-processed sausage and some fish is the perfect combination for any meal.

#SundayGunday: Hammerli Force B1

This week, were checking out the Hammerli Arms Force B1, a hunting rimfire with a target-grade pedigree.

Interests



Get the best of American Hunter delivered to your inbox.