As mentioned earlier, the .22LR is externally lubed. This used to be common prior to 1900, externally lubed cases, but the .22LR is about the only commercially available cartridge that is still around.
The lubrication is wax. It is necessary to prevent leading, and it is also helpful in blowback actions. Typically the entire case is waxed and in hot weather the wax melts in the chamber and acts as a lubricant in blow back actions. In cold weather the wax will condense in the chamber and gum up the action in time.
Wax is not soluble in water, but in hot water or soapy water it will come off.
Tumbling will mechanically remove the wax. Bad idea.
If I'm not shooting, I'm reloading.