After putting up a glassed Estes Sidewinder on an F24, Mark brought out his all aluminum rocket, "Hang 4". Power would be provided by another homemade EX motor, a 38mm 9 grain motor rated as a J330. Both the rocket and motor had flown before, though not together. Dual barometric deployment would be provided by an AltAcc altimeter. The beautiful rocket was loaded on the rail, the usual countdown, the button was pushed, and the motor ignited for a few milliseconds. Unfortunately, it then overpressurized and split open, venting the excess pressure and destroying the bottom part of the rocket and the fin can. There was a significant boom associated with the failure. There was no shrapnel; the aluminum case and airframe split open and the rocket jumped about 20 feet in the air. The plastic fin can did shatter, and fin pieces were found scattered around the pad. No propellant grains were found. The photo shows many small pieces of debris in the air around the rocket. These were probably the remains of the propellant grains. We were all at a safe distance from the rocket so no debris reached the launch team.