Mossberg 500 12 Gauge OEM 18.5 inch Matte Shotgun Barrel w/ Front Bead #90016. If you have been looking to convert your old, reliable Mossberg 500 or Maverick 88 field shotgun into a firearm that has a bit more versatility, than try this factory replacement barrel from Mossberg. This factory replacement part is made to the exact specifications and features as your original firearm which will ensure optimal fit and superior function. Increase the flexibility of your Mossberg shotgun with this factory replacement barrel. 18.5 Security Barrel. Not Threaded for Interchangeable Chokes. Mossberg 500/Maverick 88 12 Gauge Models. Note: This barrel is only compatible with the 6 Round shotguns; it will NOT fit the guns with the 8 round magazine tube.