I've seen .22 LR 's tumble out of a friends Model 18 4" Revolver. After we got home I checked the Barrel and it had enough Lead in it to make fishing sinkers!!! He had just bought the vintage M18 and failed to clean it before the Range session.

After we spent a good while cleaning it out (I had to use JB Bore Cleaner because of the severity of leading) the barrel was like new again. Now it is fine and no evidence of tumbling anymore. I doubt the prior owner ever cleaned the damned thing!