I was recently recommended the stuff to use to remove some slight rust in the bore. The stuff seems to work incredibly well, every patch has been consistently dark even in what I thought was a relatively clean bore. I have read rumours that this may be because it can strip off the metal on stainless steel bores and cause damage, does anyone know if this is true? and does anyone know if it has any effect on blueing or exterior metals? I'm also considering using it to clean up an old VZ.24 mauser.