Uncle Mike's black sling kit for Mossberg 500, allows you to simply install stud in butt stock, replace magazine cap with new adapter cap, and attach sling with quick detachable swivels provided. The 1" sling adapter comes with sling swivel and stud for the buttstock an replacement magazine cap with swivel.
Available: Sling Kit and 1" Sling Adapter.
Put these on my turkey gun this spring and they worked like a charm. With the swivel, it made moving the gun from one shoulder to another easy and no binding like the ones I had before.
I got this for my Mossberg 500 Special Purpose and it works very well. It took a little fiddling to get it installed but it could have been worse. The quick release works well but isn't that fast. My shotgun has a speedfeed pistol grip stock that was already drilled for a sling screw so that was easy. I haven't fired the gun yet so I can't say if the accuracy was affected at long range, but its a home defense weapon so I'm not worried about it either way.
I put this kit on my Mossberg 500AB 12 ga. two years ago. The first sign of a problem was when I missed a six-pointer at 40 yards. When I test fired later, I found it was shooting 12 inches low at 40 yards. I found out that the magazine adaptor caused a magazine/barrel misalignment and I couldn't adjust my sxcope enough to compensate. I put the original adaptor back on and everything is fine.