The gun is not throated for longer bullets.
I believe the twist rate of the barrel is 1:9.5, I will check when I get home (on vacation right now).
It shot the hornady 162 A max very well. Might be worth a call to HS precision to ask them their experience with their barrels withe the longer bullets. Barnes recommends a 1:9 twist which is a touch faster than 9.5. Even calling barnes and asking them how the 168 would shoot in a 9.5 barrel would be a good idea.
In terms of accuracy, this gun is phenomenal, especially at this price... you won't find a more accurate gun anywhere near this price.