I agree with gunnut308. I too use it in .308 and have never had any issues. I too am in the Southeast and have never had issues with it. Then again, I'm not one to run the ragged edge either. I also use RL-15 when competing in FTR and never had issues.
I believe the MK316 Mod 0 round the military uses calls for a 175 gr Matchking and 41.75 gr of IMR 4064 and a Lake City case. Back when this was developed, I remember guys mentioning that 4064 was chosen due to being fairly temp stable.
As for the 6.5 CM, not sure which grain bullet you're loading for. However, if shooting the 140s, I've had some really good luck with RL-16 which has been really temp stable.
