So density altitude is RELATIVE air density??
Density altitude is a way of expressing absolute density.
The term comes from flying. It's a way to express the actual density of the air (which is a function of pressure, temperature and humidity), in a form meaningful to a pilot ("Density Altitude = 3200ft" means that the density of the air is the same as Standard Atmospheric Conditions at 3200' elevation).
However I have not found the guy at the range that has been able to read his Kestral and make the first shot be any closer to zero??? The military has sophisticated instuments to accomplish this and contrary to popular belief, snipers still usually require sighting shots for long range hits. I am sure that one could spend a lot of practice time studing DA and get a lot closer to centre on first shots, but that a lot of time I'm predicting! For jetting 2-stroke engines we had a guage that expressed relative air density as a percent ...
Many (though absolutely not all!) shooters using Kestrels are relatively inexperienced shooters, who are using the best instruments they can get in an effort to get the best results they possibly can. So much of this "guys with Kestrels don't get better first sighters than guys without" could be due to this.
The instruments the military uses are not sophisticated. They are rugged, they are expensive, they are reliable - but it starts with measuring air temperature and air pressure.
BTW the same principles in selecting carburetor jets applies to the amount of effect the air has on a bullet (you're interested in either the absolute density of the air, or the density relative to a standard reference condition).
I hope not too many of the guys I shoot with read this one!! hahaha
How big is your bull???
I have a hell of a time getting a drop chart that is within a 1/4moa after inputting all the data as accurratly as possible??? maybe I'm missing something
If your input data are correct, you should be able to get to about a quarter MOA or so. You need accurate data for your m.v., your bullet's BC (preferably a G7 figure, even better Litz's data), the air temperature and your elevation above sea level. Smaller factors that you might get away with ignoring are the humidity and the barometric pressure (depends on how accurate you need your results and what distance you are shooting).
