Thanks for the information. I didn't notice a problem with the "lurching" until I started working on the base. It's possible I'm binding the wire also in that position.This fellow has some relevant info as to welder settings. If your wire seems to be "lurching" out and then burning back, then you are probably right about the tip. Note also that if you bend the lead in a short radius, the liner can bind the wire and present the same effect. Drive wheels that are too tight and/or tight wire spools can cause the same issue.
I'll pick up some tips tomorrow and try again.