Sorry for your rocket. One easy way to achieve this result is by assembling the delay backwards. If the delay o-ring is on the delay spacer instead of the delay element itself, the forward closure won't be sealed properly, leading to a blow by on ignition. The parts go together nicely this way too, so it won't necessarily feel wrong when it is assembled this way.RMS I-211, ejection went off with ignition. Destroyed my "go-to" rocket. No more RMS for me, although I know it was probably something I did wrong.
Many of us have done something like that. In my case it was the way I assembled the delay grain and o-rings in the forward closure. The o-ring must go around or against the delay grain. It must not go around the delay spacer.
Even after all these years of building RMS motors, I still tape the instructions to the table so I can see them while I assemble the motor. I’ve never used a DMS and the few malfunctions I’ve had in RMS motors were directly traceable to my mistakes.Probably but it always helps to have instructions in front of you when assembling motor.