I have a 500 Persuader that I have abused for almost 10 years now. It has the 18 1/2 inch barrel. It used to be black, but it is now more of a steel and black camo pattern. It has been dropped, thrown, kicked, tossed, had several thousand rounds of slugs, 00 buck, and bird shot, shot through it and the bead site is looooong gone. It has NEVER not fired when I pulled the trigger. It does have a little rattle in it, but the action always stays closed even with slugs in it. It cost me $228, 9 years ago. Came with a pistol grip also.
I would say VERY reliable. Supposed to be duplicates of the Milspec Mossbergs. I believe it after what I put mine through.