[JerryF504]

Honestly, to me, it doesn't look like the problem was the bullet shorting to the heatsink. To me it looks more like there was excess resistance in that connector that caused the it to melt. I had some excess resistance in one of my bullets but I caught it in time because it was on the battery side and the symptoms were obvious. Being on the motor side I'm not sure how noticable the symptoms would have been. It looks like the biggest part of your bullet that is burned off isn't even on the side of bullet closest to the heasink.