I belive that it could be recambered to 6.5-284. For me it wouldnt be practical as I think I would get more barrel life out of the 260. The other would be faster though. I also am not sure what your goals are either. It would help to know more about your rifle and also more about what you want out of the rifle.
Ahhhh... most of the 'good' bullets in 6.5mm are pretty close to 140gr, plus or minus a very small amount: 139gr Lapua, 141gr Cauterrucio VLD, 140gr JLK VLD, 142gr SMK. The longer stuff like 155gr+ aren't good for much as far as long range is concerned.
As far as 6.5-08 vs 6.5-284 in a factory gun, I guess the thought in my mind is are you going to actually realize enough velocity difference in that length of barrel? The 6.5-284 generally does a little better w/ more room to stretch it's legs, so to speak.
gents - I ran across a remington long action , with a long magazine , in a pawn shop. the barrel has been replaced , med weight, about 26", triggers been replaced , the bore is real bad, full of copper , the throat is worn , but the thing looks like it might clean up - the wood is stock no damage , but looks like they had a bi -pod.
the new barrel doesn't bind in the stock and looks good - even - and can slide a dollar to the action . the barrel is marked 260 REM - 9 , hand stamped- thought it might clean up with a 6.5/284 with out loosing length. find a replacement follower for inside the mag and I would have something to practice with , besides my 308's and another mid range rodent to deer gun with low recoil - thanks