Use of Density Altitude

[mikecr]

I see interest in using Density Altitude as measured from a Krestel in the field. Possibly due to the Tubb/S&B DTAC reticle, I don't know. Some looking for rules of thumb..Most ballistic programs don't have a DA input.

I believe there would not be any rules of thumb w/DA outside a specific bullet. Just as there aren't really any for other factors effecting drag or BC. You could identify and define an amplitude of change for YOUR bullet and temperature,using ballistic software). Same with pressure, humidity, or density altitude. But that would apply only to your bullet, and maybe not mine.

Anyway, I put together a spreadsheet which adjusts 'local BC' for changes in air density. This is what ballistic software does. I included a density altitude input that may help you in this endeavor and others.
I plan to try using DA in the field for woodchuck hunting this year. Maybe it's the way to go.

 

[DTubb]

Mike,
If you would like a copy of the DTAC instruction manual you can call SSS,8063239488) and they would send one your direction. I believe that if you learn how to plot the DA changes to your bullet /velocity combination then you will be on to a working solution.
Keep in mind that you may here the argument that DA is not a good ballstic yardstick since temperature changes effect burn rates of powder hence velocities will vary - a valid arguement with a lot of powders.
Using DA as a ballistic yardstick is a great solution when used with a temperature insensitive powder ie. - Hodgdon series then your velocity spreads from 0-125 degrees will be less than 20 feet per second,H4350 is 4 fps/Varget is 8 fps on the Hodgdon web site).
DTubb