Instead of developing drop charts for multiple elevation, temperature, barametric pressure, humidity and atmospheric changes could you just develop one set of cards with air density being the only variable? Would this work or am I way off?

That can work, but you will need a minature weather station, including temp., pressure, and humidity. Once you get relative air density, you will need to factor in the temp of your ammo and your barrel as well.

Would this Kestrel meter work?

http://www.kestrelmeters.com/kestrel-4000.htm

Would carrying your ammo in a shirt pocket at close to body temp minimize the ammo temperature issue?

How much could 100 degrees Fahrenheit variation in barrel temperature change point of impact? Any recommendations for an inexpensive means of measuring barrel temperature?

You can get to Relative air density with a Kestrel, no problem. We always carried a multi meter with a temp probe for ammo and barrel temps. Although there is probably something newer and more compact now. I always keep ammo on an inside pocket for Ultra long range shots, to minimize the impact of cold temp on ignition and velocity.

quote:

How much could 100 degrees Fahrenheit variation in barrel temperature change point of impact? Any recommendations for an inexpensive means of measuring barrel temperature?

Not an easy question to answer. I have seen barrels shoot in almost the same spot smokin hot and dead cold, less than 1/4 Moa difference at 100 yards. Not the same answer at 1500 yards, however. The same gun shot 1.25 MOA different vertically cold to hot at 1500 yards. You guessed it.... the cold shot was low.