Try winchester staball match. Ive only tested 100 or so rounds so nowhere near enough to throw my aa2520 and imr8208xbr loads out yet but things are promising. Im shooting the 77TMK at 2.30 oal from an 18" barrel with average velocity a little over 2700fps. Accuracy is on par with 8208 but not as good as my aa2520 load so far. However according to hodgdon staball match has anti copper fouling additives and is supposed to be consistent in different temperatures even though its a "ball" powder. Its made in the USA so availability is pretty good. Ive not had to hunt it down or put any stock notifications in. I just go to my local shop and its on the shelf. If it works well in my 6x45 then I probably wont worry about buying imr8208xbr again.Just received notice powder valley has xbr 8208 in 8#.
and it shows out of stock now.