Most factory 6.5X68's have a 12" twist, OK for short bullets, but not for long ones.
: Most 6.5X68's will out-shoot .264 Win Mag's for velocity, each loaded to max pressures for the brass, as RWS brass is stronger than US brass.
: In a good barrel, a 60gr. capacity case will shoot along with either for top speed, as those large cases are a bit big for the bore size. It takes a lot of "Extra" powder to get another 50 or 100fps from them over some smaller cases.
: In other words, the 6.5X284 will generally be seen to produce near-equal ballistics in a good barrel, if properly throated for the bullets being used.
: A 24" 6.5X68 will get 3,300fps from 120gr. XLC's, but then so will a 62gr. case that is about 22gr. less capacity.
: I cannot see burning 22+gr. more powder to get virtually the same ballistics. In the upper reaches of the 6.5's velocity, 100fps muzzle vel. increase makes NO difference to the game.
: I feel anthing larger than the old '06 case's capacity is too much for that bore size. There are better case shapes in that capacity as well. I'm assuming the 6.5X65 is the 'basic' '06 type case. That should work just fine.
: A .260Rem lengthened .143"(60gr. capacity) will give the same 3,300fps with 120gr. XLC's that the 6.5X68 excells with on our B.C. Moose - my Daughter's rifle did just that.