As Cam says, I have a 6XC. It was built on Valkyrie action with a 28" Pac Nor barrel, Timney trigger unit and sits in an aluminium stock that I made. I wanted to have a magazine feed so the action isn't as stiff as it could be if I'd gone for a single loading one.
I've not had the time or opportunity to shoot at long range yet but the results from shorter ranges are impressive. Our club runs a 200 bench rest comp and I won it using the 6XC with a centre to centre group of 0.277MOA. This was with Vit550 and 105 Lapua bullets. I will be trying Reloader 17 soon as this is said to be good with the 6XC.
The bonuses with 6XC are that it was designed by Tubb to shoot to 1000 yards, the cases (Norma) are available without fire forming or resizing and if you're not into reloading Norma factory ammo is available. I used some factory ammo to start with as unprimed cases were out of stock, it had a very consistent MV.
The case base is 308 Win so it will go into any action designed for 308" and it will mag feed if that's what you need. (If you are going to mag feed use the Magpul mags, not the AICS.) I made a single loading block for use when not using the magazine.
Some shooters are using 115gr Berger bullets at 3250fps MV. Even with this high velocity barrel life is expected to be over 3,000 rounds. With lower MV or lighter bullets such as 105gr it should be a fair bit more.
My rifle: