I don't load SMK 77's to very high velocity for my 20" rifles. Accuracy and velocity are not interdependent on their own. You do not need a high velocity to get small group sizes.
Quite often a lower velocity will provide smaller groups downrange IF that velocity matches the bbl node. You will always find more than one bbl node across a good range of velocity so there is no real reason to load to the point of primer piercing.
High muzzle velocity is needed only for maintaining supersonic speed to a longer useful range AND reducing wind drift comparatively.
I typically like to see no more than 2650-2700 fps from a 77gr in a 20" bbl.
My pet SMK77 load goes 2665fps out of my 1:8 JP AR.
LC brass (weight segregated and uniformed)
WW SR primer
I put 24.5gr Varget under the SMK69 at 2.245" COAL and get 2700ish fps and same point of impact at 200 yards as the SMK77 load. I like not having to change my scope settings on my multi-gun competition rifle
Here are some groups shot with the SMK77 load in my JP 1:8 20" mid-weight bbl.
BTW, 77gr boattails (VLD's actually) are still wallowing around and not fully spin stabilized at less than 125-150 yards so they tend to group larger than they ought to at 100 yards. 55gr flatbase is your best bet if all you want is the smallest group at 100 yards
10 shots at 200 yards
5 shots at 100 yards