This code shows blood and gore and should not be attempted to those who are weak against the viewing of violence. But for those who choose to read on, here is the code:

To get the blasting heads, stay away from the enemy from 4-6 squares. Get a mercenary who has an 87 on marksmanship and has a good, powerful weapon that has at least a 25+ damage and 20+ range. If all goes well, his head should blast.