I can think of a couple of things to check. Make sure the front screw from your scope base is not touching the bolt head. Check the barrel nut to make sure it's tight. Also, the action should be free floated on the sides and especially the rear tang.
Do they come bedded in the Mcmillian stocks? If not, it may need bedded.
I use win brass, cci br2, varget at 44.5-45 and 175 SMK at around 2700 in my 10fp.