Just picked up a Glock 30 SF on Thursday. I have about 300 rounds throught it. I notice that after each 25 rounds or so, I get a blue-black residue on the muzzle end of the slide and frame. I assume this is not a big deal but it is different than my experience with my other 6 Glocks. Since this is my first .45 caliber, I thought I would conslut with Forum members that have more experience. I am shooting American Eagle 230gr FMJ.