I think your problem is you have too many 308's You need to ship me one of those and your problem is solved.
Like has been said every gun is different. Head space has tolerances, like any thing else that is manufactured. You can either full length size for both or keep each separate and neck size. Having a Handi, you will need to keep your loads tamed down a bit to neck size. If you start loading them up to the top of the range, case stretch can get to the point, where full length sizing is needed to chamber it again. I have used different head stamps to aid in keeping loads separated + labels of course.
Good Luck and Good Shooting