DD, sorry your question got lost in the shuffle. You might try forming the base of your cartridges from a different grade of paper than the cartridges themselves. Ordinary white packing tissue works. Drill a hole into a block of wood about the diameter of your cartridge base, i use a brad point bit because it leaves a flat bottom to the hole. Sand the hole smooth, chamfer it lightly, and treat it with wax or silicone to prevent the cartridge sticking.
Punch out disks of tissue paper about 1/8 larger diameter than the cartridge base, and with the cartridge on its forming mandrel, lightly glue the cartridge lip, and press a disk into hole in the wood block with the mandrel, like capping a beer bottle only upside down.
You don't need to soak the tissue in anything. You could probably substitute flash paper for tissue if you felt like buying some online.
For glue i like partially evaporated nitro varnish, you can get it at any paint store. Nitro based clear nail polish works too, but it's difficult to find these days.
Punch out disks of tissue paper about 1/8 larger diameter than the cartridge base, and with the cartridge on its forming mandrel, lightly glue the cartridge lip, and press a disk into hole in the wood block with the mandrel, like capping a beer bottle only upside down.
You don't need to soak the tissue in anything. You could probably substitute flash paper for tissue if you felt like buying some online.
For glue i like partially evaporated nitro varnish, you can get it at any paint store. Nitro based clear nail polish works too, but it's difficult to find these days.