Greg McGee, who has 78 lifetime points in IBS 1,000 yard benchrest, used a short-action Remington with the .300 Weatherby, which is longer still than the Win Mag. (McGee went bronze in 1995, the first year there was IBS 1KBR.) Clay Spenser did all his work.
Since the 6-XC is just a trifle shorter than a .22/250 necked up to 6mm, you're not only good to go, but have the action length most would deem correct.