Ultra 7 or 9, they will both sound good and be hearing safe on a bolt gun. I went with a 6.5 Ultra 9 a few months ago but I want to pick up a Ultra 7 for another build I'm starting soon. I would also like to have an Ultra 5 primarily for hunting use, but that may be another year or two down the road.
I currently use a Rugged Surge on my 260 which sounds great and has minimal poi shift from can off/on. The only down side is it's a bit heavy but doesn't bother me if I'm not packing it a long distance.