There is no doubt that a 260 or 7'08 would be the better choice because of the heavier bullet for elk. Colorado allows the 243/6mm to be used for elk hunting with a minimum bullet weight of 85 grains,so a 100 grain partition would no doubt be better than the 85. It surprised me to see that in their regulations as they are known for being strict and sometimes hardasses when it comes to hunting in their state. I guess they base their regulation on requests from hunters and rely on a well placed shot with a tough bullet at high velocity. No matter what you chose, teach him to hold shots to a maximum of 200 yards with these lighter calibers. That 257 ackley with partitions should do the trick.
I wish him lots of luck and use a rest.
