I can not get the bore of my HK 45 clean. No matter what I do there remains some fouling near the muzzle. The fouling seems to be in 3 spots near the grooves. I've tried running patches with hoppes 9 down the bore letting it sit a bit then the running clean patches til they come out clean. Even after the patches come out clean the fouling remains. I've also used a bore snake and a plastic brush with solvent to loosen the fouling with no luck. I've also tried bore scrubber as a last resort. Any other things I could try?