I would suggest that you send the barre, or shotgun, to Briley and as them to remove the choke and convert the barrel to the Briley thin wall choke system. As for why, it's because polychokes are ALL rather heavy and will upset the balance of a fine shotgun. BTW, there are web sites out there that are devoted to Shotgun Handloading using classic components and paper roll crimped hulls. So if you want to use your shotgun occasionally it is possible to build ammo that is compatible with a polychoke. Note, the kit's for doing these loads are mostly whackamole kits, so hand loading will probably only yield about 25-40 hulls per hour.

BTW, if having this done is too expensive then just make that shotgun a wall hanger and purchase a new Mossberg, or used Remy 870, to shoot.