On all of my firearms (pistols, revolvers, center fire rifles and black powder) when cleaning, I first run patches with powder solvent to get out most of the carbon then run brass brush followed by patches until patches come clean. However if I run the brass brush again, followed by patches. the patches are dirty. No matter how many times I repeat this cycle the patches are dirty following the brass brush. I even wash the brush with solvent. What gives? It's driving me nuts.