IMO! 
needing temperature stable powders for hunting ammo is way overblown. Which I assume is what youre making with the 123 SST. Nothing wrong with using single based extruded powders but, for hunting ammo, I find it overkill and unnecessary. You need to get out past 600 yds or so before large extreme spreads (temperature sensitivity) in velocity start to have any effect on group size. FWIW: all of the factory Grendel ammo Ive ever pulled apart, including Hornadys 123 SSTs, has been loaded with a ball powder! Just saying
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Of the 4 ball powders you listed, I really like Lever with 120-130 weight class projectiles. With A2520 next, followed by CFE 223. Have no experience with BL-C2.
needing temperature stable powders for hunting ammo is way overblown. Which I assume is what youre making with the 123 SST. Nothing wrong with using single based extruded powders but, for hunting ammo, I find it overkill and unnecessary. You need to get out past 600 yds or so before large extreme spreads (temperature sensitivity) in velocity start to have any effect on group size. FWIW: all of the factory Grendel ammo Ive ever pulled apart, including Hornadys 123 SSTs, has been loaded with a ball powder! Just saying
..Of the 4 ball powders you listed, I really like Lever with 120-130 weight class projectiles. With A2520 next, followed by CFE 223. Have no experience with BL-C2.