Just noticed some grey streaks inside the barrel of my new Glock 19 Gen 4. They are at the muzzle end and look like they go a few cm into the barrel. Can't see if they extend all the way to the chamber end. They also come out of the barrel past the crown onto the angled bit. See attached photo. I've only fired 90 rounds of FMJ and I've tried cleaning it with brush and solvent but the grey streaks are still there. Is this normal? Should I be worried?