I currently work in a production shop primarily working with .25-.50 mild steel. Our shop has a millermatic 252. I'm having trouble with the machine constantly blowing back the wire into the tip when I strike an arc. The other issue I'm having is the wire not feeding smoothly while I'm welding. I can feel the wire in the lead rubbing and catching. I've replaced the liner and still had the same results. It's annoying when welding pipe and my welds have to pass pressure and dye tests and in constantly having to stop because the welder is having issues. Does anyone know what the problem is? I don't think the welder can handle the load but my bosses ( who aren't Welders) won't listen to me.