I have a rifle in .243 Winchester with a Savage 110 action that I am thinking about converting over to a .308. I for a E.R. Shaw barrel that I want to use and it currently has a Shaw on it but in 243. How hard is it to convert it? Do I only need the barrel seeing as the 243 is just a necked down version? I know i would have to make sure the head spacing is all good and everything, but what else do I need to know?