I have the 18.5" 590A1, with the sling stud in the magazine end cap. When the cap and stud are both tight, the hole in the stud is off to the side, which makes the sling hang uneven. To get it straight, I losened up the stud. It won't fall out with the sling swivel attached, but it seems like it would be better if tightened. If I tighten up the stud, I can back off on the mag end cap about 1/4 turn to straighten it up. Y'all have any experience with this?