RL 22 is probably the worst powder that I have ever tried in my 270 wsm, I had to burn a pound and a half to find that out, it is very temperature sensitive, it's lot to lot performance is erratic. IMR 4831 works best in my 270 WSM with 130 gr Barnes xlc bullets, Ramshot magnum gives me top velocity with Barnes 150 gr X bullet and 150 gr Nosler partitions, I am getting 3/4" groups with the Barnes 150's. Going to test the partition load for accuracy this weekend, I put about 400 rounds through my rifle before I found the right loads. I am getting around 2980 fps with the 150's and 3250 fps with the 130's.
I guess that's why they make so many different powders. What works great in one rifle doesn't work well in another.
As for the alleged temperature sensitivity issue in RL22 and MagPro, if it exists at all it is a non-issue for me since all of the rifle whitetail season in Northern Minnesota takes place when it's darn cold outside. Work up a good load in the summer and then check your zero before whitetail season when it's cold. Never get a pressure problem and in my years of handloading I've never seen a significant shift of zero when it gets cold.
Nothing else really matters other than that first shot out of a cold barrel anyway.
