Burning propellant ejected
Over pressurization. Forward closure blew off.
About 5 seconds. The instructions need to be changed on the bonded grain motors to explain that each grain needs to have epoxy totally covering the grain to inhibit the burning of the end of the grain. I was under the false impression that the epoxy was just to hold the offset cores in alignment. I have talked to Karl and Gary at AT, and they mentioned they are amending the instructions.