Casing burned through just above the nozzle/aft
It burned through just sheet the rocket lifted past the rail. Tim Lehr recognized immediately what I had done... I flipped the two o-rings (fat ring on top instead of on bottom. I sent the day before helping a dozen guys build 38mm motors where the fat o-ring goes on bottom, then went to build my H128 without reading directions and put the fat o ring on bottom, even though the 29mmm hpr reloads put the fat o-ring on top... I didn't file a report with the manufacturer because as soon as Tim told me what I had done, I knew he was right, and it was because I just didn't double check the directions since I was in the habit of putting the fat o-ring on bottom.