The 6.5X284 has several advantages when chambered in a rifle with a magazine long enough to allow bullets to be seated out so they don't take up powder space. Its powder capacity is about ideal for the 6.5mm bore - not over-bore capacity like the 264 WinMag, which is notorius for short barrel life, yet enough capacity to allow high enough velocity for long-range shooting. Winchester had discontinued production of the parent 284 case, but demand brought them back into at least limited production. As noted above, Norma has begun to produce cases, though they will probably be in short supply until High Power shooters get all they want. The selection of match-quality bullets is another plus. One pitfall I've read about is that many of the chambering reamers for this cartridge are a little too big at the case head, causing cases to expand and primer pockets to loosen prematurely. This can be overcome with a properly dimensioned reamer. There has been quite a lot of discussion about this cartridge over on the High Power board at GunTalk.