If your current .308 barrel is in good condition and is shooting well.........then why are you even considering changing it??
If, however, the barrel is shot out or the throat is eroded to the poiont you are going to swap it out,.... then go for whatever caliber you want!
The .260 is a fine caliber, but so is the .308.
If your current barrel is good....leave it alone and spend your money on a good used rifle in 6.5 x 55 (near identical to the .260 and plenty of ammo on the shelves) ........then you'll have both!!!