As PKL say the Federal 85 gr BTHP is a very good round. But it does a lot of damage to the animal/deer you shoot ok for Charlie. I think the x bolt has a 1 in 10 twist so 85 should work great. I shoot the 85 gr in my Ruger 1 in 9 twist rifle and get on well with them. I'll be trying the federal 100 gr soft point this weekend. I'll let you know how i get on with them. They are about half the price of 85 gr and easy to get hold of too, un like the 85 gr.
I use RWS 100g soft point (Its called T mantle i think) in my X bolt .243, never tried anything else. On the paper they are very accurate. I've had a few Does with it this winter and all have dropped on the spot bar one which went 20 yards and that was still a high heart/lung shot. They leave a nice clean hole on the exit and do very little damage to the meat. Really happy with the set up on the hole.