You can make the 6.5-284 work but you'll have to seat the bullets way deep to make if feed an probably a little massaging on the mag lips or feed rails.
Not to sure what you shooting at target wise , critters? peper? and how far.
The 243 Ackley will get you to 1000yds pretty easy in that action for paper or small varmints and small deer type critters out to 500yds.
also the 260 will work well in that action , run a 140gr A-max out at 2800ish fps and it'll get you to 1000yds and deer out to 600yds.
The 260 is a small step behind the 6.5-284 velocity wise and you'll get better barrel life easier feeding and less recoil. Run the balistics of a 140gr A-max at 2900fps (which is pretty easy to get I hear) up against a 300Win mag shooting a 190gr SMK at 2900-3000fps. Youll see that they are very close in drop and wind drift and the 260 flat smokes the 308 at long range, Ask Shawn Carlock.
But if its just paper and small vermints your after the 6mmBR with a 1-8 twist will make a good round with long barrel life almost no recoil and good reloading choices
