I looked at my Mossberg 500 today and on the barrel very close to where in goes into the reciever, there is this white crispy stuff that keeps forming. Not a lot but it happened before and i wiped it off and i just found it again today. I wiped it off again and put some oil on it. Does anyone know what this could be? It is where the back of the rib ends and I found it in the same spot both times. It is in this area where there is a corner, its not on a flat surface.