During a pressure test on the choke and kill line of a subsea stack, an incident occurred that resulted in property damage. When the test pressure reached 14,000 psi, the internal threads within the Kick Out Stablock ring stripped and failed to hold. Once the lock ring threads failed, the force was transferred to four ¾” studs located on the underside of the threaded locking ring. The ¾” studs failed and the high pressure hose was blown off the test cap. The design test pressure of the threaded lock ring was 22,000 psi. Risk assessment was performed and implemented risk mitigation required the hazard area to be barricaded prior to the test.