13 3/8″ casing was run into the hole and cemented in place. The float collar and cement were drilled out with a mud motor and the BOP was closed to test the casing. The pressure was brought up to 1500 psi with the rig pump. Following the test the driller attempted to bleed down the pressure through the standpipe. Pressure would not bleed back through the mud motor, so the HCR was opened to bleed back through the choke manifold. The driller instructed everyone to stand back as he opened the BOP. Pressure blew the inner bushings out of the rotary table. No injuries resulted.