Hey Kathwacckkk, my new GM LRH barrel did that to me the first two times I shot it. Got some very light rust color on a clean patch a few days after shooting. Don't know why. It no longer does it. I cleaned it real well before I ever shot it to remove any factory preservative, and went through my regular soap and water cleaning after shooting it, followed by drying and oiling with Rem Wonder Lube. Got me to wondering if I had it dry enough before running the final oil patch down the bore.