First-time gun owner. S&W .357, 686-6 frame. I've put just shy of 1000 rounds of 38 SPL 158GR through the barrel. I clean the gun within a day or two of using it. Cleaning consists of cleaning fluid, patch cloth, and a plastic-bristle brush. Tonight I cleaned the gun and noticed the muzzle-end of the barrel looked odd. I'm unsure if I'm looking at barrel damage or projectile residue. Can anyone chime in and let me know if I'm just facing a thorough cleaning session or something more costly?