I'm shooting the Berger 180gr VLD at 3185 fps out of a 27" Rock barrel with a 1-9" twist chambered in 7mm RUM.
I shot 5-3 shot groups at 500 meters yesterday afternoon with an average group size for all 5 groups being .47 moa.
The smallest group was .23 moa and the largest was .61 moa.
This being said I think your twist rate is just fine, your barrel just might not like the 168gr Berger or you might want to try them with a .010" jam into the lands as this is what I'm doing with the 180's.
I also shoot the 175 SMK's at 2975 fps out of a 27" Broughton 5C barrel with a 1-9" twist chambered in 7mm WSM
, they shoot real well, shot a 7.13" 15 shot agg at 1K earlier this month.
Hope this answers some of your questions,
Wayne aka WAMBO