Bobby Gunn: The King of Underground Bare-Knuckle Boxing

Warning: This video contains graphic imagery and profanity. 

In the underground world of bare-knuckle boxing, Bobby Gunn is the king. He is 73-0 in fights that have taken place in parking garages, warehouses, repair shops and other secret locations. 

Bleacher Report takes a guided tour into this secret and illegal "fight club" and sees what it takes to make it in the "purest form of combat sports."