The carbon fiber is on the top edges of the channel and the foam is in the bottom. It’s super easy to sand out these channels. Stocky’s said somewhere in this thread that the carbon layup is the same for all barrel profiles, so you don’t need to worry about sanding through it. Just wrap some sandpaper on a long socket or something else appropriate and go to town.What is being sanded? Foam fill?
I have a 3B on order which I’m not expecting to see for a month or two (late Feb follower here) which will house a Tikka lite contour for now, but I’ve got a recently acquired d18 contour barrel sitting in the safe so a bit of sanding may be needed down the road.