I went to amazon and there were a ton of choices for citric acid. Which do you use for case cleaning and what concentration?I really like citric acid for case cleaning. It works great and doesn't alter the metallurgy of the brass. I get it from Amazon for cheap. It also is a great surface rust remover. You can wipe it on and it will dissolve the oxides (rust) but not the base metal. Bear in mind that it will remove bluing though so don't use if for cleaning any blued parts.