One more thing on the .260, as Karl said, you need a fast twist to stabilize the high BC slugs that make these round shine.
I believe that most .260s on the market have slower twists than desirable. Ruger used to have some new production M77 MKIIs in their warehouse that have 22" barrels and 1 in 8 twists. I got one of them. Their current production compacts with 16" barrels won't help you much.
Agree with Karl on long barrels to get the most out of the round but to do so, I think you'll have to go custom or rebarrel an existing gun. Don
