a firing head adapted to connected between a coiled tubing and a perforating gun , is sized and shaped to enable it to move freely within a tubing string in the wellbore , may be actuated by fluid pressure within the coiled tubing , and includes a circulation and recirculation feature wherein wellbore fluid may be circulated through the firing head between the coiled tubing and an annulus around the tubing string , the circulation taking place either before or after detonation of the perforating gun . three firing heads are discussed . one such firing head is a circulation direction firing head . the cdf firing head circulates fluid from the wellbore to the coiled tubing and depresses a piston . then , fluid pressure from the coiled tubing lifts the piston uncovering locking balls and propelling a firing pin to a booster of a detonating cord detonating the cdf firing head . fluid circulation from the coiled tubing to the wellbore annulus begins after the cdf firing head detonates . another such firing head is a circulation ball firing head . the cbf firing head circulates fluid from the wellbore to the coiled tubing , receives a ball , and uses fluid pressure in the coiled tubing to lift a piston , uncover the locking balls and detonate the cbf firing head . another such firing head is a ball actuated circulation firing head . the bcf firing head circulates fluid from the wellbore to the coiled tubing , receives a ball from the wellbore surface , and uses fluid pressure in the coiled tubing to push a piston downwardly which uncovers the locking balls and detonates the bcf firing head . recirculation is permitted after the firing head detonates .