I am looking for some tips. I recently purchased a Smith 629, which is my first wheel gun. Had a great time shooting it, then went home to clean and the powder (lead?) at the front of the cylinder will not come off no matter what I try. First I tried CLP, then Gunscrubber but neither one does a thing to those marks no matter how much elbow grease I put into it. The gun is stainless finish. Tips?