MIG wire breaking at the TIP

[performance]

Ray,
Sorry to contradict you but most common flux core is negative, straight polarity. See here:

http://www.weldingtipsandtricks.com/...ux-core-1.html

Reverse polarity will cause melting into the tip as well on some flux cores. Dual Shield flux wire can be run DC+. There may be the odd brand that recommends a + polarity on flux core, but most that I am familiar with use DC-.