Just store them with out the nipple. I have a shooting box for each of the Remington's and another one for the plains rifle and Hawkins.

We make dry firing caps for the center fires using those little erasers for the maniacal pencils. Run the case thru the die and deprime it then add the eraser in the primer pocket. Could do some thing similar with a BP for 209's, And with thought I could come up with some thing for a #11 nipple.

With the ML remove the bolt screw with the bolt in the uncocked position, take it apart clean it then install again with the retaining screw removed then add the screw and it will stay uncocked too

Al