I have some solvent left, that we found in Dad's shop when cleaning it out after he passed away. This solvent is green in colour, and was in an obscure can - no markings. We've used it to get the nipples and breeches out of a few guns now. We set the barrels down into the solvent, with a few ounces poured insize as well, when nipple seats were plugged. In around 7 days, the plugs and nipples come out easily. I surely wish I knew what it was. Green- anyone have any ideas? It sure is good stuff.