Since we are talking lead babbits here, I will relate my first experience with one. Not me using, but watching!
In 1970 bought a brand new 5 inch model 27, my pride and joy. A Skeeter gun. But, as you turned the cylinder it would get harder, and then easier, so that is was more difficult to turn on about two cylinders. At this time I was a young officer with about three years experience, and we were attending our second National PPC match in Jackson, MS. I took the brand new gun, unfired at that moment, into the trailer where there were two or three Smith factory personnel working on officer's guns all the while chatting away while their hands worked.
When it was guns turn for their attention, I explained the problem, and he took the gun in hand and worked the cylinder around a few turns, then to my complete surprise and astonishment, took the gun in left hand, muzzle skyward, picked up the round babbit that he called German Silver, and whacked the face of the right side of the cylinder with a very solid impact, I think he hit it two or three times. He then checked the rotation of the cylinder and handed it back to me and said it had a burr on it and now it didn't. It worked perfectly after that.
I was shocked to see a gun that I had just bought, a premier gun of the line, and at that time pretty hard to find, just whacked by a lead bar! Not a mark on the gun, but I just barely avoided fainting!
I attended armorer's school in 1986 and now have my own set, along with the other armorers tools. I still shy away from striking guns with the babbits, though!