The 6.5 Creedmoor was developed around a 28" barrel and the 28" works fine. I started using a 28" in early 2008 with the 6.5 in my match rifles and stuck with it. When I asked Dave Emery, one of the developers of the 6.5 Creedmoor, in 2007 what barrel length to get when starting to build my rifle he said "28 inch" so I took that and used it. I did try a 26" once with a set back and it worked fine too for accuracy. The longer length is just free velocity. There was an old Rifleshooter "test" that showed the Creedmoor lost velocity after 24". Biggest BS around. Flawed test but spewed all over the internet as fact. Hell even a little .223 is still gaining velocity after 24" so anyone thinking that a round with almost twice as much powder is also is just fooling themselves.
As to what would work for you, well that's up to you. If shot from the bench then no reason not to go longer. I shoot PRS style matches and run a 28" with a 3" brake on it without a problem. You can go 24" if you like too. It's only 600 yards so you won't lose much. A thought though is that you can always cut a longer barrel down if you don;t like it but you can't add on barrel to a shorter barrel.
As to what would work for you, well that's up to you. If shot from the bench then no reason not to go longer. I shoot PRS style matches and run a 28" with a 3" brake on it without a problem. You can go 24" if you like too. It's only 600 yards so you won't lose much. A thought though is that you can always cut a longer barrel down if you don;t like it but you can't add on barrel to a shorter barrel.
