What started me thinking about paper this was the waxed paper sealing better than plastic to the chamber. I do not know. Also I had concerns of blow back with plastic being hard on hinge pins with these guns. All these guns are tight and on face. The other question is 1 superposed I own made in 1952. I know none of these chambers were made with plastic in mind. Maybe I am concerned about nothing, just do not want any problems.