Yup, the label on the jug say it contain vinegar. This stuff cuts the hard crusty build up on breech plugs better than anything i have ever tried. With Hoppes i have to use a brass brush and scrub the breech plug, and when i get done there is still a bit of carbon left.I also need to use a 1/8" drill to remove carbon from the hole below the primer pocket. The exterior of the breech plug looks like new after soaking in the all purpose cleaner, and reaming the hole with the drill takes no effort at all; seems like a pipe cleaner could be used instead of the drill.