My first wirefeed was without gas so it used flux core wire, that is, a flux was present inside a hollow core wire. This flux will leave a residue during welding, requiring that you clean each weld, especially between passes if you are building up an area. The flux can also interfere with certain paints, etc if it comes out of the weld later. I finally got a 225 Lincoln MIG that uses 10 pound solid wire spools. The gas shields the weld from air during welding and makes a nice metal bead, no flux, no cleaning. Great for my kind of welding where I have to weld up my holes, etc. Once you get the wire speed and voltage right (amps) then you can just move the gun along almost in a straight line, with very little weave, unless you're filling a big crack. Make sure the gas attachment has a solenoid that only opens when the trigger is pressed to weld, also that the tip is not electrically hot until the trigger is pushed. I saw one where the gas ran all the time and used too much, and its safer with the electically cold tip. You may want infinite heat adjustment - some only give you two or three heat choices and they may not always match your job. Good luck!
