Honestly, you have a GREAT round -- .308 --, It will handle mostly anything (non dangerous) under 200 yards, and If your looking for "more power"... the .270 ain't gonna give you that.......
35 whelen is a good round, but if I was you, I'd look hard into 338 win mag, its just a nice all-around North american round. 338 is great for short range / long range / mid range. Don't get me wrong, your 308 will pretty much do most of what the 338 can, but the 338 is just...... more power !!!!
and another thing, you have been using your 308 for a long time i suppose, so you are very used to the rifle and its feel......If you go a head and get a .270 your gonna have to shoot it for some time to get your self REALLY used to it.
Stay with your 308, and if you got the cash, look up walmart.com on a nice 338 win mag (I prefer winchester rifles)
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