I read another similar post a few yrs ago and started to record and measure DA when shooting groups. Then my DA meter quit and I got real busy running shoots, business, family, etc and sort of forgot about it. I still measure temp and humidity when I shoot.
We don't shoot straight groups so the data is kind of hard to correlate with groups/tune and I really only shoot 1-2 times/month. Our range in CR is about 1000' with the temp and humidity fairly constant. Temp varies from -4'C to 8'C in the winter with 60-90% humidity. Spring & fall we get 6'C to 20'C with humidity about the same. The one relay that we shoot 100yd groups, the group sizes are fairly consistant thoughout the year. Then again none of us are really that good and shoot enough groups on a day to day basis to track. Most of our shooters don't care either.
Like I said before, I don't shoot enough groups with one gun to correlate the data. Sometimes having too many guns is a problem. Don't tell my wife I said that.
I went to a BR Turkey Shoot in Rock Creek, BC a few yrs ago and worked up a load there for a custom ppc and a 22-250 that I was shooting on the coast. Rock Creek is 2010' elevation and was -5'C. DA was 0. In CR at 1000' and 0'C DA is approx -700. I had to go up 1 gr of H322 in the ppc to get it to shoot and didn't change the load for the Factory Savage 22-250 at all. Kinda inconclusive. I do think old Beggs is right though. DA has got to effect tune.
Another link with a handy chart.
http://en.wikipedia.org/wiki/Density_altitude To answer your question "have any of you bothered to track density altitude?" Rick, I started to but fell off the wagon
cheers
Greg