Thanks for your service! I was on the FPO side of the house. As stated above, a practice lock with a grub screw installed above each pin stack would be the ideal way to go. You could load just one, or all chambers with what ever you want to throw in there. If you can't pick it open, just empty the chambers, and reload them differently for another challenge. Good luck!
My fleet of NR2003 online race cars.