Is the rear mount suppose to be lose? Have mossberg 500 20 barrel — 2 Answers

The rear mount is not supposed to be loose but it was too loose for my Mossberg Maverick 88 (Mossberg 500 clone) 20" barrel. Either NcSTAR made an error in manufacturing or it is possible they made their measurements from a Mossberg shotgun that had a slightly larger diameter magazine tube. My solution was to use one or more layers of 3M 3340 aluminum foil tape to shim the rear mount. The tape is 0.09 mm thick, strong and designed for high heat applications (up to 300 °F). Cut the tape long enough to go around the inside circumference of the mount and cut it slightly less in width so it does not show. Smooth the tape on the inside of the mount to ensure that the adhesive takes hold and then the rear mount should install securely.