I haven't drilled any cores. I've only converted delay motors to boosters. I cut the motor tube off just above the clay cap to make access easy, then used brass tools to remove the cap, ejection charge, and delay. I then glued the section back on to get a full length motor. I didn't have a brass bit and wouldn't have used one on the initial mods anyway because I didn't want to go to deep and take out some propellant. I've also limited my tasks to summertime so the high humidity would help eliminate static electricity issues. PPE is a must.

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I love sanding.