If you are not inclined to do much to your rifles , Tikka is a Good place to start! I know they make .260s and 6.5x55s. 6.5x55 brass is the cheapest of all the Lapua made 6.5s and magazine length is a non issue. .260 is my fav. but Am considering others for a future rebarrel......
The .264 and 26 add noise and expense when it is just not needed. unless you shoot to 400yds and just want to aim and shoot. Any caliber requires some drop charts and either a reticle or knob twisting past that.
Do know if I helped ,but any of the middle 6.5s will make you smile!