Hello Curt, the comment about polarity was a bit of a shot in the dark, I don't have any evidence that would support an issue such as his, due to polarity. I guess you could say that based on the information he had supplied up to the point where I included the polarity item, I was running out of options for things that could be causing the porosity. Polarity is one of those things that I don't often notice issues with because I don't typically run on the incorrect one(please don't misunderstand me, I am not saying that I am perfect in any way, but I do have plenty of readily available information to determine the correct choice), occasionally I will have students make mistakes and we can see the sorts of issues that can show up, but in this case I can't say that I have personally experienced what would result from an incorrect polarity use with the 308 rod. Maybe I'll have to do some playing and see what happens, if I do I'll try to include some additional information. Best regards, Allan