Digger,
I own a 12BVSS in .223 Rem as well. From what I read the 68 or 69gr bullets are not too heavy for 1:9 twist.
I just started reloading my .223 ammo, and have been playing with the 52gr SMK bullets and H335 powder. I did try my reloads at 200 yards a couple of times, but no I'm not getting 1" groups. Maybe the rifle is capable of 0.5 MOA at 200 yds, but I'm not there yet as a shooter or reloader.
My Lyman Reloading Manual lists 26.0 gr of Varget as the accuracy load for the 69gr SMK. The Sierra Reloading Manual has 26.5 gr of N540 as the accuracy load for the 69 gr SMK.
Congratulations on your good shooting and I hope it gets even better.
Marc