Put your standard bolt back the plastic ones dont seal very good on the valve guide orings and make it so the poppet opens before the bolt is fully shut, and lowering of dwell make the bolt come back quicker so it opens the hole to the breech before it should all resulting in possible breaking of paint.
one way to check if bolt is working properly is to put two balls in the fire and fire once the second ball should not jump out of the breech if it does then you have a valve guide oring oring problem.