6.5 grendel sbr powder. Choices

[myrifle]

My first choice would be N135. You will get complete powder burn at 12" with really low SD's. I used this with Sierra 107's and the SD's were below 5. That was measured over 20 shots and 6 different charge weights.

I'd try H322 or Xterminator as well. Again, you should get close to or complete powder burn at 12".

If loading close to max charge weights, I wouldn't worry about temp stability unless hunting when it's in the 80's or 90's.

All modern powders are completely burnt before the barrel reaches the gas port. Even on carbine length gas systems.

If it wasnt the gas block and gas tube would clog up very quickly with sunburnt powder.