I have tested twice with placing a charge in the rocket, at the top of the fin can, below the PML piston. The first test the charge was small and it push the payload/nose cone off without moving the piston. The second test, I used a bigger charge. The payload/nose cone went flying off and pulled the piston out. The piston wasn't blown out.
The expanding gas behind the piston is moving past the piston. How can this be?
The piston slides easily. I even use baby powder to help it slide and it slides easily. It is tight enough that it doesn't rattle/wobble in the tube. When blowing with my mouth I can blow the piston out. With a charge, the piston doesn't move. How is this possible?
Thanks
Mike