The scratches on the swivel are just from clipping the bipod on and off a couple times. They are purely cosmetic. The bipod clip just struggles to open far enough to smoothly go over the swivel. The bipod also has nothing circular on it that could leave an impression of this nature, being the circular shape that it is. So the only thing I could think would be that possibly it is a stress crack from putting the bipod on too tight. That being said I don't have it any tighter than any other rifle I own and I have had no problems to date.