You can definitely run a BA Quad Rail on a Mossberg 500, particularly the one made by Black Aces Tactical. These rails are designed to fit the Mossberg 500, as well as the 590, 590A1, and Maverick 88 models, and typically do not require gunsmithing for installation. The installation usually involves using provided hardware to replace the trigger pins and secure the rail to the barrel clamp.
Installation process
Remove the existing forearm: Take off the original factory forearm.
Replace the trigger guard pin: Remove the factory pin near the trigger guard and replace it with the new pin and spacers included in the kit.
Install the barrel clamp: Slide the barrel clamp over the shotgun's magazine tube and barrel.
Mount the rail: Slide the quad rail over the clamp and use the provided screws to attach the rail to the clamp. The rear holes of the rail will align with the new trigger pin.
Tighten everything: Ensure all screws are tight and secure, as some users have noted they can back out over time.

yes they fit and work just fine on the Mossberg 500

Hi Jason and welcome. I run a Black Aces Quad Rail and love it. They have become hard to find but available here: mountsplus.com/mossberg-500-rail-black-aces-tactical.html -------------- Cheers, stay safe and enjoy!