If the "hinge is rather loose" it should be attended to before you attempt to shoot this gun with low pressure ammo only of course. A technique I've used in the past to clean up damascus barrels is to coat them with Simonize car wax which is mildly abrasive and does a good job of removing surface tarnish without disturbing the original finish.
Jim

The 2nd Amendment IS an unalienable right.