If you're worried about tightening up your grouping, by a trainer .22 (in your case the Savage Mark-II) and set it up similar to your .270. My Mark-II will print .8" groups at 100 yards. It's easier and cheaper to work on shooting w/ an accurate .22!!

As for the ammo itself in your .270, the only thing I can tell you is to buy a box of each different loads and see what your rifle likes the most. One of my savages LOVES 168gr SMK's whereas the other one is a hair more accurate with the 175SMK's. Some rifles like some ammo more than others.