Skinny, one of my hunting buddies uses a 6.5x55 with 95 V Max's for woodchucks. Works pretty well, but I wouldn't pick it as a 600 yard bullet- too light for the caliber.
I think you want to stay with the 6's.
The 6mm AI or the 6-284 would kind of interest me, but I don't mind single loading- at 600 yards, if they charge ya, it takes a long time for 'em to get to you.
