Jim,

Check out Mule Deer's posts regarding RL-26 and the 270 Win, in the "Ask the gun writers" forum. He started testing for temperature sensitivity last year, through the winter (even in zero temp ranges) and also in the summer. Throughout he has recorded consistent velocities. As to the 300 Win Mag, I don't recall if his tests included it, but there were many guys posting in that thread that were using many other calibers. I'll post a couple of the threads below.

https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/11560214/1

This one is specifically related to cold weather testing. https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/11644886/1

I have found it to be very consistent and accurate in my 270 with 150 gr partitions and 130 gr E-tips (dime size groups and less) - and 7mm-08 with 150 gr Balistic tips. Many are finding that RL-26 seems to have a niche with heavy for caliber bullets - good accuracy with excellent velocity. So far, I am very pleased with what I have seen in my rifles with RL-26.

gundog