RE: 6.5x.284
Actually the 6.5X.284 has slightly greater powder capacity then either the .260 Remington or the 6.5X55. Does that make it any better? Only the individual wanting one can answer that question.
And in truth the 6.5X.284 is no longer a "true wildcat". Several years ago Sako and Norma teamed to make it factory loaded. Though on a "very limited" basis. And if I'm not mistaken...Norma still produces small batches of 6.5X.284 from time to time! (Worth looking into.....if you're thinking about building a 6.5X.284.
Also, the 6.5X.284 has had considerable success of late at long range riflery (1000 yards) matches. A very well balanced cartridge!
Once again....best of luck!