I don't know exactly how to weigh in on this as the temp/velocity variation stuff I bumped into mostly occured with the 7 Rem Mag and 7828, or IMR 4831. I would notice that velocities were substantially higher in the summer than the winter (10-20 F). But I also noticed that IMR4831 showed LESS variation in the 270 than it did in the 7 Mag and at the time sort of concluded that it was related to load density, ie there was less space left over in the 270 case than the 7 Mag. VERY UNSCIENTIFIC but it was my half-arsed guess.
Shot a whitetail buck in Alberta this fall; AIR TEMP was about 25 below zero. Load was 60-RL22-130 Nosler partition in a Kreiger barreled M70 270 Win.The deer died. Also had along a M70 in 264; load was 62-H4831-125 Nosler Partition which did 3300 back home.Nether rifle needed to be rezeroed and test shooting was done in bitter cold.
I worry about temp sensitivty too but I burn a lot of RL22 and H4831 and only note that once I get to a load with either powder, I shoot it year round to watch that point-of-impact thing. I don't know what else a guy can do except establish a general trend in the load behavior, shoot it a lot and get skeptical when a real "spike" occurs in the load's general pattern.I will also note that match shooters in my club push the hell out of their AR's in 223 to get heavy bullets stable at 600 yards; there are lots of blown primers during the summer months when temps are high; but some of them are burning Hodgdon Extreme powders, and don't have any problems...
