After applying the CA finish, I take the barrels off the mandrel/bushings and dry sand the barrel ends with 400 or 800 wet & dry. Sand them by hand, placing the sandpaper on the lathe way so it is nice and flat. Then remount the barrels on the mandrel and wet sand.
I also found that sanding off the excess on the ends also prevents the CA chipping or delaminating when the hardware is pressed on.
I use HDPE cones (like eliminators) that I made, for my finishing. The CA will coat the HDPE but won't stick like it does to metal bushings. On 7mm barrels you need to score the CA so it will snap off the HDPE neatly. Larger barrels the CA will snap where the cone meets the brass tube without scoring.
TonyO