I dropped my 391 piston into the milky white, citrus-scented goop, pulled it out a quarter of an hour later and with a little brushing, the caked residue flaked off. All of it. For good measure I dunked the piston from an old S&W 1000 with the same results. Then I threw in a ported choke tube caked with powder reside and plastic wad material. Some scrubbing and voila, it was spotless. After that I found myself searching though my choke tubes looking for cruddy ones to clean. I hate to admit this is my idea of big fun, but there it is. If anybody out there has a miracle cleaner they swear by, I'd like to know about it.