Shorter bullets with the wrong powder can produce horrible groups in an otherwise accurate rifle. That's been my experience with a .243, .308 and 350 rem mag.
I'd suggest avoiding the lighter bullet loads. While I understand the frustration with shooting groups that large, I've had factory ammo and hand loads do just that in the above mentioned rifles. And I've shot sub moa with the same rifles when I found the combo the gun liked, mostly handloads but also with some factory loads.
