Never say never..... But We have used golf ball shells in aluminum foil where the charge and the ball is rolled into a aluminum shell and rammed down the barrel, And I have keep those shells for days and sometimes weeks before using them and no issues of static electricity.
But more important to this a couple of photos would be nice.. I have a 1/2 scale golf ball french 75 cannon that recoils. I did not build it.. (that is why it looks so darn good) but here is a youtube shot before I packed it in the car. It was built by one of the great cannon makers of all time, One who's powder I am unworthy to set off..