Yeah, I believe a few years ago, the company tried the use of metal core wire for the track welder and for other spray applications. I think what happened was the track welder operator had it at a bad setting that caused the weld to fall out or peel out of the joint. After that ONE mishap, the engineers took away the wire and had it use solid wire since then. They are not very educated in the welding aspect or the properties of metal. I know we have had a boat load of problems with solid wire for years, but we still use it. I think that at the right settings, the metal core wire can produce a very clean, strong weld.