What variable to change when truing my weapon

[mikecr]

But you'll want an accurate program for long work, as you approach a mile and beyond you'll find every little detail matters.

While true in a sense, this is a perspective that feeds the mass delusion in shooting among us.
For hunting, LONG WORK is not relative to distance, but to the shooting system, killzone, and the many conditions of each shot.

Just to be clear, by using absolute pressure aren't making the elevation irrelevant which is important to account for? I know that Station pressure is pressure at your actual location which is what you want.

I use absolute pressure(Station) because this is what I measure and what is actually used in ballistic software.
The real terms for air density are -> station pressure, temperature, and relative humidity
All other terms are calculated/converted/converting, and by far most shooters flub this all up.

If you don't measure air density parameters in the field, you can let the conversions begin, but be careful with this. It's easy to make errors with inputs to your software(which must assume you know what you're doing)..
So you can determine real altitude using GPS, or a tikki pole outside the diner, and then carefully adjust from 'standard conditions for altitude'(which is assumed until manually adjusted) with local/actual temperature & humidity.

I'll try to attach a spreadsheet that helps understanding of this. It's not for field solutions but shows what ballistic software does internally to your BC inputs based on your air density inputs. It also provides for G7 BC conversion if desired.

 

[seidersjoden]

Thanks for the conversion table, didn't realize it changed that much, from earlier posts, that Cold Bore program, I assume to get a BC for extended long range you can use one BC for out to the transonic zone and then another BC that accounts for the bullet as it goes through the transonic zone??

 

[mikecr]

What 'cold bore program'? You're leaving the reservation here..
There are no predictions for BC through transonic. This would have to be measured as dynamic stability comes into play.

 

[coues52]

Great post ! this why I really enjoy this site ! Danny