I've been using the included tip (3.?mm) that came with my Checkpoint and Hakko soldering stations for years and never had an issue soldering anything. When I switched to the 5.2mm tip everything was much easier and faster to solder. 10 and 12 gauge are very easy to solder. Regardless of the type of solder (I'm still using some 60/40 flux core Radio Shack solder) going to a wider tip will help speed things up. I still keep the smaller tip on my Checkpoint iron just in case I need to solder smaller gauge stuff.