It is a mig welder. and the longer the stick out less power its gonna have. can you say voltage drop. use like 1/4-3/8 stickout. and pre heat the metal. after all welding is just dumping heat into it. so by pre heating you get more penitration. as for the stick out run the wire out of the gun for 3-4 and then have it hit the plate, it will just start to glow red. thats voltage drop the less stick out the more volts you have to weld.
its not mig. It is a flux cored wire. GMAW and FCAW, two totally different processes.
http://www.harborfreight.com/cpi/ctaf/Category.taf?CategoryID=292they all come with a flux cored wire. you cant put a bottle and mig wire in a 90 dollar HF welder.