std7mag said:Keeping it a 30-06, or changing to something else will not matter one bit with the inletting issue you may have.
It's all in the barrel contour. Aka shape of the outside of the barrel.
He shouldn't have any issues with the barrel contour if he orders a stock inlet for a Mark X with a factory sporter contour. If you look at the pictures you can tell it is just a sporter contour barrel, nothing fancy. Same thing if the OP replaces the barrel and keeps the stock, just order the factory sporter contour and there won't be any issues.