I have questions about when to use contact tip setback (tip-to-nozzle)... or when someone would someone want to use a different styles of tips from the standard style (such as Cutback tips, Heavy Duty tips or Tapered tips)? I know the tips for my spool gun have a cutback in the face of the tip and I'm really curious as to the why of this...

Is there advantages and disadvantages to each such as sheilding gas coverage, CTWD (contact tip to work distance), "heat vs. cooling" in short circuit transfer, globular transfer or spray transfer?

I was told use a normal tip with flush to 1/8 inch setback for short circuit transfer... and a Heavy Duty style tip with 1/8 to 1/4 inch setback for spray transfer... but I've only guessed at the whys.