Fellas,
I've heard this same thing from numerous shooters. I'm a competitive shooter for many years now in IBS/NBRSA/PA 600 and 1000yd clubs. I've fired in matches from NY to NC and from the east coast to as far west as Colorado. I personally use R22 in my 30 caliber Heavy class(HG) rifles. And I use H4831SC in my LG class rifle.
After keeping an eye on this for years, most shooters here have it nailed down. Yes it is affected some, but not as much as everyone would like you to beleive. Shiredude I think hit the nail on the head. One bad day or even a couple doesn't mean anything. But when you start looking at data over several years and many different ranges I don't think R22 is any more sentives than any other powder for your particular case.
The one exception to my theory is with WW748 in my 223. It shoots like a house a fire in the hot summer months here in NC. But take it out in the cooler winter months and it will open up the groups considerably. I've been experimenting with Benchmark and got some good groups in the heat of the summer. Have not tried it during the winter yet. Isn't cool enough here yet.
But I have taken the same successful loads in my BR rifles here on the east coast and driven to Byers, Colorado or Pierre, SD at a much higher elevation, different temperature and humidity ranges and fired the same loads and still finished near the top.
I beleive with maybe a few exceptions that IF a load does go haywire on you at a different elevation, humidity, temperature... then the load probably really wasn't properly tuned to your rifle that well to begin with. Meaning, if 72gr of R22 will shoot at sea level at 90F and same humidity and I drive to Byers at 70F, elevation of several thousand feet above sea level, and humidity below 50% and still shoot the same groups at 1000yds. Then that load has a broad tune range and is very forgiving. Yes the pressure probably changed some with that much change but it didn't drop me out of my sweet spot that I had tuned for.
Maybe if I shot H1000 it might shoot at sea-level but not in Byers... then H1000 doesn't have a wide sweet spot for the tune in that particular barrel. My theory is that the powder has some to do with it but it's more in the harmonics of the barrel (your tune) that causes a particualr load to go south with a narrower sweet spot.
In my Light Gun(LG) class rifle I have used my same old faithful load of 50.5gr of H4831 (long or short cut) with bullet weighing from 135 to 147 gr and it always works and have won with it in varying conditions and many different states and elevations. That load is a great marriage in my chamber and barrel. So I don't mess with it. Well until I got to the bottom of the first 8# jug. But that is a whole other story and tests aren't conclusive yet.
In any event I look for a load with a wide sweet spot and don't really get bent out of shape about the temp, humidity etc. Now for example if the temps go way up, then I might drop my load a little just to keep the tune "centered" so that during the actual match I don't get those "where the @#$%#@ did that come from?" situation.
Steve
